World's oases threatened by desertification, even as humans expand them

Oases are important habitats and water sources for dryland regions, sustaining 10% of the world's population despite taking up about 1.5% of land area. But in many places, climate change and anthropogenic activities threaten oases' fragile existence. New research shows how the world's oases have grown and shrunk over the past 25 years as water availability patterns changed and desertification encroaches on these wet refuges.

"Although the scientific community has always emphasized the importance of oases, there has not been a clear map of the global distribution of oases," said Dongwei Gui, a geoscientist at the Chinese Academy of Science who led the study. "Oasis research has both theoretical and practical significance for achieving United Nations Sustainable Development Goals and promoting sustainable development in arid regions."

The study found that oases around the world grew by more than 220,149 square kilometers (85,000 square miles) from 1995 to 2020, mostly due to intentional oasis expansion projects in Asia. But desertification drove the loss of 134,300 square kilometers (51,854 square miles) of oasis over the same period, also mostly in Asia, leading to a net growth of 86,500 square kilometers (about 33,400 square miles) over the study period.

The findings highlight the risk climate change and anthropogenic stressors pose to these wet sanctuaries and can inform water resource management and sustainable development in arid regions. The study was published in the AGU journal Earth's Future, which publishes interdisciplinary research on the past, present and future of our planet and its inhabitants.

The birth and death of an oasis

Oases are important sources of water for humans, plants and animals in the world's drylands, supporting a majority of productivity and life in deserts. They form when groundwater flows and settles into low-lying areas, or when surface meltwater flows downslope from adjacent mountain ranges and pools. The existence of an oasis depends primarily on having a reliable source of water that is not rainfall. Today, oases are found in 37 countries; 77% of oases are located in Asia, and 13% are found in Australia.

Gui and his co-investigators wanted to understand the global distribution and dynamic changes of oases and see how they respond to a changing environment, such as variations in climate, water resources and human activities. Using data from the European Space Agency's Climate Change Initiative Land Cover Product, the team categorized the land surface into seven categories: forest, grassland, shrub, cropland, water, urban and desert.

The researchers used satellite data to look for green, vegetated areas within dryland areas, indicating an oasis, and tracked changes over 25 years. Changes in the greenness of vegetation indicated changes in land use and oasis health, the latter of which can be influenced by both human activity and climate change. They also looked at changes in land surface type to find conversions of land use.

The researchers found that global oasis area increased by 220,800 square kilometers (85,251 square miles) over the 25-year timeframe. Most of that increase was from humans intentionally converting desert land into oases using runoff water and groundwater pumping, creating grasslands and croplands. The increase was concentrated in China, where management efforts have contributed more than 60% of the growth, Gui said. For example, more than 95% of the population in China's Xinjiang Uygur Autonomous Region lives within an oasis, motivating conservation and a 16,700 square kilometer (6,448 square mile) expansion of the oasis, Gui said.

Countering human efforts to expand oases, desertification contributed to oasis loss. Worldwide, the researchers found there was a loss of more than 134,000 square kilometers (51,738 square miles) of oasis land over the past 25 years. The researchers estimate that changes to oases have directly affected about 34 million people around the world.

Overall, between gains and losses, oases had a net growth of 86,500 square kilometers (33,397 square miles) from 1995 to 2020 -- but most gains were from the artificial expansion of oases, which may not be sustainable in the future.

Long-term oasis sustainability

The study highlighted ways to sustain healthy oases, including suggestions for improving water resource management, promoting sustainable land use and management and encouraging water conservation and efficient use. These efforts are especially important as the climate continues to change, Gui said.

Humans' overexploitation of dwindling groundwater can limit oasis sustainability, as well as long-term glacier loss. While higher temperatures increase glacier melt, temporarily boosting oases' water supplies, "as glaciers gradually disappear, the yield of meltwater will eventually decrease, leading to the shrinkage of oases once again," Gui said.

International cooperation plays a crucial role in oasis sustainability, Gui said.

"Due to the unique mechanism of oasis formation, a river basin often nurtures multiple oases across several countries, making transboundary cooperation key to addressing water scarcity and promoting sustainable development," he said.

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First comprehensive look at effects of 2020-2021 California megafires on terrestrial wildlife habitat

The only thing constant is change -- isn't that how the saying goes? We know that wildlife in western forests evolved with changing habitat and disturbances like wildfire. Each species responds differently, some benefiting from openings, others losing critical habitat. What we don't know is how increasing fire severity at large scales is impacting their habitat and survival, because many species are not adapted to these types of "megafires." Researchers at the Rocky Mountain Research Station set about finding some answers. They summarize their findings in "The 2020-2021 California megafires and their impacts to wildlife habitat," a paper that published today in the Proceedings of the National Academy of Sciences.

Why California and why this time period? In 2020 and 2021, California experienced fire activity unlike anything recorded in the modern record.

When the smoke cleared, the amount of burned forest totaled ten times more than the annual average going back to the late 1800s.

Nearly half of the forests that burned experienced high-severity fire, killing 75-100% of the vegetation, and much of this fire covered large continuous areas, rather than a patchy mosaic.

California's Department of Fish and Wildlife curates a comprehensive wildlife database, mapping habitat suitability of hundreds of species across the state.

Coupling that with Forest Service records of wildfires and some fancy computer footwork gave researchers an opportunity to take a broad look at how these types of "megafires" are shaping wildlife habitat within the state.

Jessalyn Ayars, the lead author, said, "Our intent was to take a broad look to gain a better understanding of the impacts of these kinds of fires on wildlife habitat as a whole." She continued, "and since each species is different, this study provides a good jumping-off point for others to be able to focus on a single species of interest or small group of species that share similar habitats."

The fires and habitat studied were mostly located in the Sierra Nevada, southern Cascades, and Klamath mountain regions of California.

Researchers looked at more than 600 wildlife species and found that for 50 species, fires spanned 15-30% of habitat within their range in the state.

One hundred species experience high severity fire over more than 10% of their geographic range within California.

Sixteen of those species are considered species of management concern, such as the great gray owl, wolverine, Pacific marten, and northern rubber boa.

Previous research shows that some species such as great gray owls may benefit from fire in terms of foraging habitat and can be somewhat resilient, but again, the unknown is whether that benefit holds true with this magnitude of habitat change in such a short time.

Some good news is that by looking more closely at some of the details around habitat change by species, scientists learned that these fires are not disproportionately impacting habitats for species of conservation concern compared to wildlife species in general, a finding that suggests that where these species live may serve as refugia for them.

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Protect delicate polar ecosystems by mapping biodiversity

Polar regions contain vast, undiscovered biodiversity but are both the most-threatened and least-understood areas of the world.

Now scientists led by the University of East Anglia (UEA) and the British Antarctic Survey (BAS) are calling for a roadmap of polar ecosystems to fill that knowledge gap, preserve polar life and even protect "our everyday life and our planet's health." The study would map all biodiversity in those regions, from the atmosphere to the deep sea and from land to the oceans.

The authors said concerted action is required to mitigate the impact of warming on polar ecosystems via conservation efforts, to sustainably manage these unique habitats and their ecosystem services, and for the sustainable bioprospecting of novel genes and compounds for societal gain.

'Multi-omics for studying and understanding polar life', is published today in Nature Communications. The paper is co-authored by UEA, BAS and the University of Bielefeld, Germany.

Polar ecosystems are the most threatened because they are the most sensitive to global warming. They are being lost at a rapid pace and with them all the biology that provides ecosystem services and biology-driven regulation of the climate, including the carbon cycle.

Prof Thomas Mock, Professor of Marine Microbiology in UEA's School of Environmental Sciences, is the joint lead author with Prof Melody Clark, Project Leader for the British Antarctic Survey.

Prof Thomas Mock said: "Biodiversity projections for the polar regions can only be reliably constructed if we have a sufficiently profound understanding of the diversity, ecological functions, and interrelations of polar organisms, as well as their resilience to climate change.

"These remote regions play substantial, often underappreciated, roles in the carbon cycle and drive global nutrient and dissolved organic matter fluxes. Consequently, polar environmental and ecological processes are intimately connected with our everyday life and our planet's health, much of which is underpinned by the endemic biota, from viruses to large animals.

"There is strong evidence that climate-induced changes in the polar regions are already altering species distributions on land and in the sea, with major impacts on ecosystem function."

Some species have shifted poleward, which has a knock-on effect on the food chain. Polar life, from microbes to seals, whales and polar bears, largely depends on overall low temperature and a substantial snow and ice cover, which are experiencing the impacts of global warming.

In the Arctic, temperatures are rising at least four times faster than elsewhere, destabilising the Arctic jet stream and increasing the likelihood of extreme weather events including heat waves, drought and flooding in temperate regions.

On land, permafrost melting and collapsing Arctic coastlines are dramatically altering ecological interactions and biogeochemistry due to the release of millennia-old carbon stores, trace elements, nutrients and potentially even deep-frozen ancient viruses and pathogenic bacteria.

In the oceans, the increased seasonal melting of sea ice is stabilizing surface waters too much, which reduces the amount of nutrients required for primary production to take place.

Similarly, the situation in the Southern Ocean and Antarctic continent is equally bleak, particularly for the Antarctic Peninsula, which has already experienced substantial levels of warming that has increased the loss of sea ice and glaciers.

The Southern Ocean is responsible for the uptake of three-quarters of the anthropogenic heat absorbed by the ocean and up to half of the carbon drawdown. It accounts for around 40 per cent of the global oceanic uptake of anthropogenic CO2 and around 50 per cent of the total atmospheric uptake. Furthermore, sequestering carbon by the organisms living in polar seas is probably the largest natural negative feedback against climate change.

The climate impacts on biodiversity and ecosystem functioning in both the Arctic and Antarctic serve as a bellwether for the consequences of global warming, including the persistence of biodiversity on Earth.

Prof Clark said: "Sequencing technologies have massively changed our abilities to decipher how organisms work. However the uptake in polar biology has been relatively low, especially when considering the tens of thousands of species that reside at the poles and are at threat in our warming world.

"Understanding how lots of very strange organisms living in extreme cold can help answer globally questions and provide real benefits for society. Failure to act now will result in a substantial loss of knowledge regarding evolutionary adaptation to the cold."

Genomic screening not only offers the possibility of identifying populations under stress, but it can also be used for the monitoring of invasive species, thereby facilitating early interventions.

Prof Mock said: "With the cold regions of our planet diminishing, there is a real imperative to obtain full genome sequences for diverse organisms inhabiting polar ecosystems, from the deep oceans to the permafrost on land, for both the Arctic and Antarctic. This will enable the wider application of omics technologies to polar species, which will revolutionise our understanding of evolution in the cold and adaptive responses to a warming world."

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Killing remains a threat to Bornean orangutans

University of Queensland research has found despite considerable conservation efforts, the illegal killing of critically endangered orangutans on Borneo may be an ongoing threat to the species.

PhD candidate Emily Massingham from UQ's Faculty of Science managed a team of researchers which visited 79 villages across the Bornean orangutan range in Kalimantan, conducting face to face interviews with 431 people.

"Our study builds on previous research which indicated killing was one of the key reasons for orangutan population decline, alongside habitat loss," Ms Massingham said.

"The aim of our project was to understand whether orangutans have been killed in recent times, to look at whether conservation projects are effectively preventing killing, and to gain insights into community perceptions and the motivations behind it.

"It has been almost 15 years since the previous study, and we did not find a clear decrease in killings despite Indonesia's commendable efforts to reduce habitat loss.

"Thirty per cent of villages reported orangutans had been killed in the last 5 -10 years, despite the practice being both illegal and taboo -- which also makes it hard to get an accurate picture of the true scale."

Ms Massingham said Borneo's orangutan population had decreased by 100,000 in recent decades, with current estimates suggesting fewer than 100,000 animals remain.

"Our findings did not indicate that conservation projects are reducing killing, highlighting an urgent need to improve the collective approach to orangutan conservation," she said.

"Killing by humans needs to be addressed, as our findings suggest it may still be occurring and poses a real threat to the species."

Ms Massingham said orangutans have long lifespans and breed slowly, so are particularly vulnerable to population declines driven by the death of adult apes.

"Our interviews revealed some of the situations which lead to the killing or displacement of individual orangutans," she said.

"They include protecting crops and taking infant apes to keep as pets."

The researchers outlined recommendations that could improve future conservation efforts.

"Working with communities and collaborating across disciplines and projects will be key," Ms Massingham said.

"Conservationists need to work closely with individual villages to understand their needs and perspectives, identify the social drivers of killing of orangutans and implement solutions that reduce human-orangutan conflict."

Read more at Science Daily

Earth's first animals had particular taste in real estate

Even without body parts that allowed for movement, new research shows -- for the first time -- that some of Earth's earliest animals managed to be picky about where they lived.

These creatures from the Ediacaran Period, roughly 550 million years ago, are strangely shaped soft-bodied animals that lived in the sea. Researchers have long considered them enigmatic.

"It's not like studying dinosaurs, which are related to birds that we can observe today," said Phillip C. Boan, UC Riverside paleontology graduate student and lead author of the new study. "With these animals, because they have no modern descendants, we're still working out basic questions about how they lived, such as how they reproduced and what they ate."

For this particular research project, the researchers focused on understanding where in the sea the animals spent their lives.

The ancient sea was also a largely foreign place compared to today's marine environments. It was dominated by a mat on the sea floor composed of bacteria and layers of other organic materials. In addition, predatory creatures were uncommon.

Given the alien nature of Ediacaran Earth, the researchers were surprised to find an animal that lived much the way barnacles do today. A new Paleobiology paper details how Obamus coronatus, named for the former U.S. president, opted to live on specific parts of the sea floor in the company of other Obamus.

The animal averaged about a half-inch in diameter and was "shaped like a French cruller donut with ribbons on top," Boan said. It did not move of its own accord, and likely spent its entire life embedded in its preferred spot on the sea floor.

"We think about the very oldest animals and maybe you wouldn't expect them to be so picky. But Obamus only occurs where there is a thick mat, and it's a pretty sophisticated way of making a living for something so very old," said Mary Droser, UCR distinguished professor of paleontology and study co-author.

In 2018, Droser's laboratory named the Obamus in honor of Barack Obama's passion for science. Her group discovered it at an extraordinarily well-preserved fossil site in the Australian Outback, at what is now called Nilpena Ediacara National Park.

A series of storms buried the Ediacaran sea floor at Nilpena in layers of sediment, helping preserve sandstone impressions of entire animal communities that lived together there. "This way, we're able to piece together whole ecosystems," Droser said. "Looking at them is like snorkeling around on the ancient sea floor, instead of looking at a single animal in a fish tank."

For this project, the research team selected three animals found in relatively large numbers at Nilpena, and examined how they were geographically distributed.

The other two animals, Tribrachidium and Rugoconites, are also immobile creatures with no modern descendants. "They are tri-radially symmetrical, like the Mercedes Benz logo," Boan said. "And they would have lived their entire lives embedded in the sea floor, as Obamus did."

Distribution for these other two animals was varied. Sometimes they could be found living in the company of other organisms like themselves, but not in every instance. However, Obamus displayed a clear preference.

"This is really the first example of a habitat-selective Ediacaran creature, the first example of a macroscopic animal doing this," Boan said. "But how did they get where they wanted to go? This is a question we don't yet know the answer to."

The research team theorizes that Obamus were likely motivated by the need to reproduce.

"There are a limited number of reproductive strategies, especially for animals like these," Droser said. "There are more strategies today, and they're more elaborate now. But the same ones used today were still being used 550 million years ago."

Obamus likely spread itself via selective larva that preferred locations with thick microbial mat and near other Obamus. "We don't entirely understand how Obamus offspring spread out, but we know that when they picked a place to live, it was very specific," Boan said.

A deeper understanding of how life on Earth developed over time can give researchers insight into how life could develop on another planet. For this reason, Droser's lab is funded by NASA's Exobiology program.

Read more at Science Daily

The science behind the life and times of the Earth's salt flats

Researchers at the University of Massachusetts Amherst and the University of Alaska Anchorage are the first to characterize two different types of surface water in the hyperarid salars -- or salt flats -- that contain much of the world's lithium deposits. This new characterization represents a leap forward in understanding how water moves through such basins, and will be key to minimizing the environmental impact on such sensitive, critical habitats.

"You can't protect the salars if you don't first understand how they work," says Sarah McKnight, lead author of the research that appeared recently in Water Resources Research. She completed this work as part of her Ph.D in geosciences at UMass Amherst.

Think of a salar as a giant, shallow depression into which water is constantly flowing, both through surface runoff but also through the much slower flow of subsurface waters. In this depression, there's no outlet for the water, and because the bowl is in an extremely arid region, the rate of evaporation is such that enormous salt flats have developed over millennia. There are different kinds of water in this depression; generally the nearer the lip of the bowl, the fresher the water. Down near the bottom of the depression, where the salt flats occur, the water is incredibly salty. However, the salt flats are occasionally pocketed with pools of brackish water. Many different kinds of valuable metals can be found in the salt flats -- including lithium -- while the pools of brackish water are critical habitat for animals like flamingoes and vicuñas.

One of the challenges of studying these systems is that many salars are relatively inaccessible. The one McKnight studies, the Salar de Atacama in Chile, is sandwiched between the Andes and the Atacama Desert. Furthermore, the hydrogeology is incredibly complex: water comes into the system from Andean runoff, as well as via the subsurface aquifer, but the process governing how exactly snow and groundwater eventually turn into salt flat is difficult to pin down.

Add to this the increased mining pressure in the area and the poorly understood effects it may have on water quality, as well as the mega-storms whose intensity and precipitation has increased markedly due to climate change, and you get a system whose workings are difficult to understand.

However, combining observations of surface and groundwater with data from the Sentinel-2 satellite and powerful computer modeling, McKnight and her colleagues were able to see something that has so far remained invisible to other researchers.

It turns out that not all water in the salar is the same. What McKnight and her colleagues call "terminal pools" are brackish ponds of water located in what is called the "transition zone," or the part of the salar where the water is increasingly briny but has not yet reached full concentration. Then there are the "transitional pools," which are located right at the boundary between the briny waters and the salt flats. Water comes into each of these pools from different sources -- some of them quite far away from the pools they feed -- and exits the pools via different pathways.

"It's important to define these two different types of surface waters," says McKnight, "because they behave very differently. After a major storm event, the terminal pools flood quickly, and then quickly recede back to their pre-flood levels. But the transitional pools take a very long time -- from a few months to almost a year -- to recede back to their normal level after a major storm."

Read more at Science Daily

Apes may have evolved upright stature for leaves, not fruit, in open woodland habitats

Anthropologists have long thought that our ape ancestors evolved an upright torso in order to pick fruit in forests, but new research from the University of Michigan suggests a life in open woodlands and a diet that included leaves drove apes' upright stature.

The finding sheds light on ape origins and pushes back the origin of grassy woodlands from between 7 million and 10 million years ago to 21 million years ago, during the Early Miocene.

Fruit grows on the spindly peripheries of trees. To reach it, large apes need to distribute their weight on branches stemming from the trunk, then reach out with their hands toward their prize. This is much easier if an ape is upright because it can more easily grab onto different branches with its hands and feet. If its back is horizontal, then its hands and feet are generally underneath the body, making it much harder to move outward to the smaller branches of a tree -- especially if the ape is large bodied.

This is how modern day apes reach fruit, and, it's been theorized, that's why apes evolved to be upright, according to U-M researchers Laura MacLatchy and John Kingston.

But new research centered around a 21-million-year-old fossil ape called Morotopithecus and led by MacLatchy suggests this might not be the case. Instead, researchers think early apes ate leaves and lived in a seasonal woodland with a broken canopy and open, grassy areas. The researchers suggest this landscape, instead of fruit in closed canopy forests, drove apes' upright stature.

Their results are published in Science and are bolstered by a companion paper examining these paleo grassy woodland habitats, published in the same issue of the journal.

"The expectation was: We have this ape with an upright back. It must be living in forests and it must be eating fruit. But as more and more bits of information became available, the first surprising thing we found was that the ape was eating leaves. The second surprise was that it was living in woodlands," said MacLatchy, a paleoanthropologist and professor in the U-M Department of Anthropology.

The two papers grew out of a U.S. National Science Foundation-funded collaboration of international paleontologists, collectively known as the Research on Eastern African Catarrhine and Hominoid Evolution project or REACHE, each of whom focus on different aspects of early ape paleoenvironments. The study led by MacLatchy focuses on a 21-million-year-old site called the Moroto site in eastern Uganda.

There, the group, which included U-M researchers William Sanders and Miranda Cosman, examined fossils found in a single stratigraphic layer, including fossils of the oldest, clearly documented ape, Morotopithecus. Also within this layer were fossils of other mammals, ancient soils called paleosols, and tiny silica particles from plants called phytoliths. The researchers used these lines of evidence to recreate the ancient environment of Morotopithecus.

MacLatchy and Kingston discovered that the plants living in this landscape were what's called "water stressed," meaning they lived through seasonal periods of rain and of aridity. This also means that at least part of the year, apes had to rely on something other than fruit to survive. Together, these findings indicate that Morotopithecus lived in an open woodland punctuated by broken canopy forests composed of trees and shrubs.

"These open environments have been invoked to explain human origins, and it was thought that you started to get these more open, seasonal environments between 10 and 7 million years ago," MacLatchy said. "Such an environmental shift is thought to have been selected for terrestrial bipedalism -- our ancestors started striding around on the ground because the trees were further apart.

"Now that we've shown that such environments were present at least 10 million years before bipedalism evolved, we need to really rethink human origins, too."

The first clue that these ancient apes were eating leaves was in the apes' molars. The molars were very "cresty": they were craggy, with peaks and valleys. Molars like this are used for tearing fibrous leaves apart, while molars used for eating fruit are typically more rounded, MacLatchy said.

The researchers also examined the apes' dental enamel, as well as the dental enamel of other mammals found in the same stratigraphic layer. They found that isotopic ratios -- the abundance of two isotopes of the same element -- in their dental enamel showed that the apes and other mammals had been eating water stressed C3 plants that are more common in open woodland or grassy woodland environments today. C3 plants are primarily woody shrubs and trees while C4 plants are arid-adapted grasses.

"Putting together the locomotion, the diet and the environment, we basically discovered a new model for ape origins," MacLatchy said. "In anthropology, we care a lot about ape evolution because humans are closely related to apes and features like lower back stability represent an arboreal adaptation that may have ultimately given rise to bipedal humans."

Early Miocene C4 grasses and open woodlands

Previously, researchers believed equatorial Africa during the Early Miocene was thickly carpeted with forest, and that open seasonal woodlands and grasslands evolved only between 7 million and 10 million years ago.

But the second paper uses a set of environmental proxies to reconstruct the vegetation structure from nine fossil ape sites across Africa, including the Moroto site, during the Early Miocene. These proxies revealed that C4 grasses were "everywhere" during that time period, said Kingston, a biological anthropologist and associate professor in the U-M Department of Anthropology.

"This paper looks at all these sites, pulls all this data together, and says, 'Look, no matter how you evaluate the data, there's no way you can escape the fact that all these proxies are converging on the same place -- namely, that these environments are open, and they're open with C4 grasses," he said.

"For the first time, we're showing that these grasses are widespread, and it's this general context of open seasonal woodland ecosystems that were integral in shaping the evolution of different mammalian lineages, including and especially in our case, how different ape lineages evolved."

The nine sites are scattered across eastern equatorial Africa, enough to develop a "regional picture" of what the sites' landscapes looked like in the Early Miocene, Kingston said. During this time, the East African Rift was forming. Earth was pulling apart. As a result, the entire region was uplifted, causing huge variation in topography, and therefore, regional climate and vegetation.

"There's mountains and volcanoes, there's cliffs and escarpments and valleys," Kingston said. "The landscape is just physically highly variable, and that, no doubt, is related to the vegetation heterogeneity."

To reconstruct the paleoenvironment at each location, the researchers used carbon isotope analyses of ancient soil organic matter, plant wax biomarkers and phytoliths found at each site. The carbon isotope analyses revealed that a wide range of plants lived in the grasslands, ranging from those that comprise closed canopy to wooded grasslands.

The wax biomarkers -- left over from the waxy material that protects leaves -- also indicate a large variety of shrubs and trees as well as grasses. Phytoliths -- microscopic biosilica bodies that give plants their structure as well as a defense against being eaten -- can tell the researchers the proportion of C4 grasses at a given site and provide further evidence for abundant C4 grasses.

After using these proxies to rebuild the paleoenvironments at these nine sites, the researchers found that C4 grasses were abundant across eastern equatorial Africa, and were a key part of the landscape's heterogeneous habitats. Their data also pushes back the oldest evidence of C4 grass-dominated habitats in Africa and globally by more than 10 million years.

"The findings have transformed what we thought we knew about early apes, and the origin for where, when and why they navigate through the trees and on the ground in multiple different ways," said Robin Bernstein, program director for biological anthropology at the National Science Foundation.

Read more at Science Daily

Ancestral variation guides future environmental adaptations

The speed of environmental change is very challenging for wild organisms. When exposed to a new environment individual plants and animals can potentially adjust their biology to better cope with new pressures they are exposed to -- this is known as phenotypic plasticity.

Plasticity is likely to be important in the early stages of colonising new places or when exposed to toxic substances in the environment. New research published in Nature Ecology & Evolution, shows that early plasticity can influence the ability to subsequently evolve genetic adaptations to conquer new habitats.

Sea campion, a coastal wildflower from the UK and Ireland has adapted to toxic, zinc rich industrial-era mining waste which kills most other plant species. The zinc-tolerant plants have evolved from zinc-sensitive, coastal populations separately in different places, several times.

To understand the role of plasticity in rapid adaptation, a team of researchers lead by Bangor University conducted experiments on sea campion.

As zinc-tolerance has evolved several times, this gave the researchers the opportunity to investigate whether ancestral plasticity made it more likely that the same genes would be used by different populations that were exposed to the same environment.

By exposing the tolerant and sensitive plants to both benign and zinc contaminated environments and measuring changes in the expression of genes in the plant's roots, the researchers were able to see how plasticity in the coastal ancestors has paved the way for adaptation to take place very quickly.

Dr Alex Papadopulos, senior lecturer at Bangor University explained:

"Sea campion usually grow on cliffs and shingle beaches, but mining opened up a new niche for them that other plants weren't able to exploit. Our research has shown that some of the beneficial plasticity in the coastal plants has helped the mine plants to adapt so quickly."

Alex added,

"Remarkably, if a gene responds to the new environment in a beneficial way in the ancestral plants, it is much more likely that that gene will be reused in all of the lineages that are independently adapting to the new environment. Phenotypic plasticity may make it more likely that there would be the same evolutionary outcome if the tape of life were replayed. If we understand the plastic responses that species have to environmental change, we may be better equipped to predict the impacts of climate change on biodiversity."

Read more at Science Daily

Wood-eating clams use their feces to dominate their habitat

Deep beneath the waves, tiny clams with shells usually about as big as a pea bore into pieces of sunken wood. The wood is food for them, as well as a home. These rare, scattered, sunken pieces of wood support miniature ecosystems where different wood-boring clam species can live in harmony for years. But in a new paper in Marine Biodiversity, researchers found that one group of wood-boring clams has evolved a unique way to get the wood all for itself: building chimneys made of poop.

"There are two challenges every sea creature has to face: getting pure water in, so you can get oxygen to your gills, and getting rid of your waste. Because nobody wants to live in their poop. But here are these clams living with theirs, and actually thriving," says Janet Voight, Associate Curator of invertebrate zoology at the Field Museum and the study's lead author.

Scientists can put wood on the seafloor, return months or even years later, and recover it with "an amazing array of animals," says Voight; other times wood that has been submerged for the same amount of time comes up so gnawed and bored-through that you can crumble it in your hand. This difference was a mystery, and Voight wanted to know why.

She took stock of the wood-boring clam species present in reports of sunken wood from all over the world, and she noticed a pattern. "There are six main branches in the wood-boring clam family tree, and every woodfall that was bored so heavily it was crushable by hand turned out to have been bored by a species from the same single branch of that family tree," says Voight. She says she was surprised by this finding -- "that's not supposed to happen, you just assume that all wood-boring clam species, which tend to look pretty similar, bore into wood the same way. And yet, here's one group that's doing something totally different."

Scientists had suggested that the extra-chewed-up wood was due to lots of larvae happening to be present nearby, or warmer water temperatures, but it turns out, the very nature of the clams may be responsible. Voight noted all of these extra-efficient, related species have a common trait where the sun don't shine. As the clams dig and move into their boreholes in the wood, they fill the space around them inside the holes with their own feces.

"They don't do it on purpose, their anatomy makes them do it," says Voight. "When these clams bore into wood, their little shell does the boring." Meanwhile, the clams' siphons, tubular appendages for taking in water to get oxygen and expelling waste, stick out behind them. "In most wood-boring clams, these two "in and out" siphons are equal in length and stick out into the water column," says Voight. "But in these related hyper-nasty borers, the siphon for expelling de-oxygenated water and feces is short; it stays inside the borehole in the wood. As a result, says Voight, "they poop in their borehole. They just have to, unless they really, really push." The waste stays right there with the clam, forming a chimney that wraps around the siphon.

That animals would evolve an anatomy that keeps them in such close contact with their own waste, is surprising, says Voight: "It sure isn't very hygienic, and yet they show no evidence of immune problems. They're healthy, they're clearly going to town on the wood. So why did they evolve this way?"

She and her colleagues hypothesized that these fecal chimneys might cue larval settlement: that their free-floating larvae might be able to detect the poop and make their way to it to make a home alongside members of their own species.

But that still leaves the problem: even if a poop chimney serves as a beacon for other members of their species to join them on their wood, how can these individuals survive as more and more larvae settle and the environment becomes filthier and oxygen becomes less available?

"This group of species of clam has been shown in previous studies to be unusually tolerant of low oxygen," says Voight. They also have additional adaptations, like a mucosal lining of their fecal chimneys, and a substance like hemoglobin in their blood that picks up more oxygen; both may reduce the risk of sulfide poisoning from the waste. Taken together, these adaptations allow these speciesto survive in conditions that would make non-related wood-boring clams sick. The end result is more wood for the chimney-producing species to eat, live in, and for their offspring to settle on, unbothered by competitors.

Beyond just solving the mystery of the gross chewed-up wood with an even grosser solution, Voight says that the study illustrates the importance of looking at ecology with an understanding of how different species are related to each other.

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Dinosaurs were on the up before asteroid downfall

The findings provide the strongest evidence yet that the dinosaurs were struck down in their prime and were not in decline, at the time the asteroid hit.

Scientists have long debated why non-bird dinosaurs, including Tyrannosaurus rex and Triceratops, became extinct -- whereas mammals and other species such as turtles and crocodiles survived.

The study, led by an international team of palaeontologists and ecologists, analysed 1,600 fossil records from North America. Researchers modelled the food chains and ecological habitats of land-living and freshwater animals during the last several million years of the Cretaceous, and the first few million years of the Paleogene period, after the asteroid hit.

Paleontologists have known for some time that many small mammals lived alongside the dinosaurs. But this research reveals that these mammals were diversifying their diets, adapting to their environments and becoming more important components of ecosystems as the Cretaceous unfolded. Meanwhile, the dinosaurs were entrenched in stable niches to which they were supremely well adapted.

Mammals didn't just take advantage of the dinosaurs dying, experts say. They were creating their own advantages through diversifying -- by occupying new ecological niches, evolving more varied diets and behaviours and enduring small shifts in climate, by rapidly adapting. These behaviours probably helped them to survive, as they were better able than the dinosaurs to cope with the radical and abrupt destruction caused by the asteroid.

First author, Jorge García-Girón, Geography Research Unit, University of Oulu, Finland and Department of Biodiversity and Environmental Management, University of León, Spain, said: "Our study provides a compelling picture of the ecological structure, food webs, and niches of the last dinosaur-dominated ecosystems of the Cretaceous period and the first mammal-dominated ecosystems after the asteroid hit. This helps us to understand one of the age-old mysteries of palaeontology: why all the non-bird dinosaurs died, but birds and mammals endured."

Co-lead author, Alfio Alessandro Chiarenza, Department of Ecology and Animal Biology, University of Vigo, Spain, said: "It seems that the stable ecology of the last dinosaurs actually hindered their survival in the wake of the asteroid impact, which abruptly changed the ecological rules of the time. Conversely, some birds, mammals, crocodilians, and turtles had previously been better adapted to unstable and rapid shifts in their environments, which might have made them better able to survive when things suddenly went bad when the asteroid hit."

Senior author, Professor Steve Brusatte, Personal Chair of Palaeontology and Evolution, School of GeoSciences, University of Edinburgh, said: "Dinosaurs were going strong, with stable ecosystems, right until the asteroid suddenly killed them off. Meanwhile, mammals were diversifying their diets, ecologies and behaviours while dinosaurs were still alive. So it wasn't simply that mammals took advantage of the dinosaurs dying, but they were making their own advantages, which ecologically preadapted them to survive the extinction and move into niches left vacant by the dead dinosaurs."

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Bee study: Both habitat quality and biodiversity can impact bee health

Efforts to promote the future health of both wild bees and managed honeybee colonies need to consider specific habitat needs, such as the density of wildflowers.

At the same time, improving other habitat measures -- such as the amount of natural habitat surrounding croplands -- may increase bee diversity while having mixed effects on overall bee health.

Those are the key findings from a new analysis of several thousand Michigan bees from 60 species. The study looked at how the quality and quantity of bee habitat surrounding small farm fields affects the levels of common viral pathogens in bee communities.

"Future land management needs to consider that broadly improving habitat quality to benefit pollinator community diversity may not necessarily also benefit pollinator health," said University of Michigan biologist Michelle Fearon, lead author of a study published online Nov. 30 in the journal Ecology. The other authors are from U-M and the University of Washington.

"To promote pollinator health, we need to focus on improving specific habitat quality features that are linked to reducing pathogen prevalence, such as planting greater density of flowers," said Fearon, a postdoctoral fellow in the Department of Ecology and Evolutionary Biology.

Bees are indispensable pollinators, supporting both agricultural productivity and the diversity of flowering plants worldwide. But in recent decades, both native bees and managed honeybee colonies have seen population declines, which are blamed on multiple interacting factors including habitat loss, parasites and disease, and pesticide use.

As part of the work for her U-M doctoral dissertation, Fearon and her colleagues netted and trapped more than 4,900 bees at 14 winter squash farms in southeastern Michigan, where both honeybees and wild native bees pollinate the squash flowers.

The bees were analyzed for the presence of three common viral pathogens. Consistently, lower virus levels were strongly linked to greater species richness, or biodiversity, among local bee communities. The number of bee species at each farm ranged from seven to 49.

Those findings, published in February 2021 in Ecology, provided support for what ecologists call the dilution effect. This controversial hypothesis posits that increased biodiversity can decrease, or dilute, infectious disease transmission.

But an unresolved question lingered after that study was published: Was biodiversity truly responsible for the observed reductions in viral levels, or was there something about habitat quality that drove changes in both bee biodiversity and viral pathogen prevalence?

"Many studies have shown that high-biodiversity communities are ones with low rates of infectious disease. But we also know that better habitat quality often leads to greater biodiversity," said study co-author Chelsea Wood of the University of Washington, a former Michigan Fellow at U-M.

"So which factor is actually driving down disease risk: biodiversity or habitat? Do high-biodiversity communities dilute disease prevalence? Or do communities in high-quality habitat have healthier hosts, who are better at resisting infection? Our data show that some apparent 'dilution effects' could actually have nothing at all to do with biodiversity."

Previous studies have demonstrated that habitat factors can directly influence both an animal's nutritional status and the strength of its immune system, which in turn can influence its susceptibility to pathogens. For example, Eurasian red squirrels living in fragmented habitats host greater gastrointestinal parasite burdens than those living in continuous forest habitats.

To get to the root cause of their Michigan bee observations, Fearon and her co-authors generated models allowing them to rigorously disentangle the effects of habitat characteristics on patterns of pathogen prevalence.

They reexamined the previously collected bee data and added new information about local and landscape-level habitat. For the study, the researchers defined high-quality bee habitat as areas that provide sufficient quantity and diversity of floral resources (both pollen and nectar) to sustain good pollinator nutrition.

At the local level, floral richness (meaning flower species diversity) and floral density were the key indicators of high-quality habitat. At the landscape level, proportion of "natural areas" surrounding farm fields and landscape richness (meaning areas with more land cover types) were the key characteristics. Natural areas included deciduous, evergreen and mixed forest; herbaceous and woody wetland; shrubland; grass pasture; and wildflower meadow.

The researchers found that habitat can have both positive and negative impacts on pathogen levels in bee communities. This is evidence for what the authors called a habitat-disease relationship, where habitat quality has a direct impact on bee health.

In general, a higher proportion of natural area and a greater richness of land cover types were associated with increased viral prevalence, while greater floral density was associated with reduced viral prevalence.

"Areas with greater floral abundance could provide better pollen and nectar resources for bees to help them resist or fight off infection," said study co-author Elizabeth Tibbetts, a professor in the U-M Department of Ecology and Evolutionary Biology who was Fearon's dissertation adviser. "Additionally, greater floral abundance may reduce the effective foraging density of pollinators and result in reduced pathogen transmission."

More natural area was also associated with higher bee species diversity, which in turn contributed to reduced, or diluted, viral prevalence.

"Most importantly, we found that greater habitat quality in the surrounding landscape was a key driver of the dilution effect that we previously observed," Fearon said. "This provides evidence for a habitat-driven biodiversity-disease relationship, where habitat quality indirectly impacts bee health by altering bee species diversity.

"But different habitat-quality metrics impacted patterns of viral prevalence both positively and negatively. This means that habitat quality has the potential to decrease or increase viral prevalence in pollinators depending on the relative strengths of the habitat-disease and biodiversity-disease pathways.

"So, it is important to consider how improving specific habitat quality measures may impact bee diversity and bee health in different ways."

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Animals are key to restoring the world's forests

As UN climate talks close in Egypt and biodiversity talks begin in Montreal, attention is on forest restoration as a solution to the twin evils roiling our planet. Forests soak up atmospheric carbon dioxide and simultaneously create habitat for organisms. So far, efforts to help forests bounce back from deforestation have typically focused on increasing one thing -- trees -- over anything else. But a new report uncovers a powerful, yet largely overlooked, driver of forest recovery: animals. The study by an international team from the Max Planck Institute of Animal Behavior, Yale School of the Environment, the New York Botanical Garden, and the Smithsonian Tropical Research Institute examined a series of regenerating forests in central Panama spanning 20 to 100 years post-abandonment. The unique long-term data set revealed that animals, by carrying a wide variety of seeds into deforested areas, are key to the recovery of tree species richness and abundance to old-growth levels after only 40-70 years of regrowth. The article, published in Philosophical Transactions of the Royal Society B, is part of a theme issue focused on forest landscape restoration as part of the UN Decade on Ecosystem Restoration.

"Animals are our greatest allies in reforestation," says Daisy Dent, a tropical ecologist from MPI-AB and the study's senior author. "Our study prompts a rethink of reforestation efforts to be about more than just establishing plant communities."

The report also notes that situating regenerating forests near patches of old growth, and reducing hunting, encourages animals to colonize and establish. "We show that considering the wider ecosystem, as well as features of the landscape, improves restoration efforts," says Sergio Estrada-Villegas, a biologist now at Universidad del Rosario (Bogotá, Colombia) and the study's first author.

Seed dispersal by animals is key to forest expansion. In the tropics, over 80% of tree species can be dispersed by animals, which transport seeds throughout the landscape. Despite this, forest restoration efforts continue to focus on increasing tree cover rather than reestablishing the animal-plant interactions that underpin ecosystem function. "Figuring out how animals contribute to reforestation is prohibitively hard because you need detailed information about which animals eat which plants," says Estrada-Villegas.

The forest at the Barro Colorado Nature Monument (BCNM), in the Panama Canal, offers a unique solution to this problem. In one of the best studied tropical forests in the world, generations of scientists at have documented frugivore interactions to understand which groups of animals disperse which tree species.

In the present study, the team led by Estrada-Villegas and Dent examined this unique long-term dataset to determine the proportion of plants dispersed by four groups of animals -- flightless mammals, large birds, small birds, and bats -- and how this proportion changed over a century of natural restoration.

Their results offer the most detailed data of animal seed dispersal recovery across the longest timeframe of natural restoration. "Most studies examine the first 30 years of succession, but our data spanning 100 years gives us a rare glimpse into what happens in the late phase of restoration," says Dent.

The study found that young regenerating forests were made up mostly of trees dispersed by small birds. But as the forest aged, trees dispersed by larger birds increased. Surprisingly, however, the majority of plants were dispersed by terrestrial mammals across all forest ages -- from 20 years old to old growth. "This result is quite unusual for post-agricultural regenerating forests," says Dent. "It is likely that the presence of large tracts of preserved forests near our secondary stands, coupled with low hunting, has allowed the mammal populations to thrive and to bring an influx of seeds from neighboring patches."

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Global bird populations steadily declining

Staggering declines in bird populations are taking place around the world. So concludes a study from scientists at multiple institutions, published today in the journal Annual Review of Environment and Resources. Loss and degradation of natural habitats and direct overexploitation of many species are cited as the key threats to avian biodiversity. Climate change is identified as an emerging driver of bird population declines.

"We are now witnessing the first signs of a new wave of extinctions of continentally distributed bird species," says lead author Alexander Lees, senior lecturer at Manchester Metropolitan University in the United Kingdom and also a research associate at the Cornell Lab of Ornithology. "Avian diversity peaks globally in the tropics and it is there that we also find the highest number of threatened species."

The study says approximately 48% of existing bird species worldwide are known or suspected to be undergoing population declines. Populations are stable for 39% of species. Only 6% are showing increasing population trends, and the status of 7% is still unknown. The study authors reviewed changes in avian biodiversity using data from the International Union for Conservation of Nature's "Red List" to reveal population changes among the world's 11,000 bird species.

The findings mirror the results of a seminal 2019 study which determined that nearly 3 billion breeding birds have been lost during the past 50 years across the United States and Canada. The lead author of that study is also an author on this global status report.

"After documenting the loss of nearly 3 billion birds in North America alone, it was dismaying to see the same patterns of population declines and extinction occurring globally," says conservation scientist Ken Rosenberg from the Cornell Lab, now retired. "Because birds are highly visible and sensitive indicators of environmental health, we know their loss signals a much wider loss of biodiversity and threats to human health and well-being."

Despite their findings, study authors say there is hope for avian conservation efforts, but transformative change is needed.

"The fate of bird populations is strongly dependent on stopping the loss and degradation of habitats," says Lees. "That is often driven by demand for resources. We need to better consider how commodity flows can contribute to biodiversity loss and try to reduce the human footprint on the natural world."

"Fortunately, the global network of bird conservation organizations taking part in this study have the tools to prevent further loss of bird species and abundance," adds Rosenberg. "From land protection to policies supporting sustainable resource-use, it all depends on the will of governments and of society to live side by side with nature on our shared planet."

Information is key, and study authors point out that the growth of public participation in bird monitoring and the advent of easy-to-use tools, such as the Cornell Lab's eBird database, make continental-scale breeding bird surveys, distribution atlases, and abundance models possible and help inform conservation efforts.

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Early human habitats linked to past climate shifts

A study published in Nature by an international team of scientists provides clear evidence for a link between astronomically-driven climate change and human evolution.

By combining the most extensive database of well-dated fossil remains and archeological artefacts with an unprecedented new supercomputer model simulating earth's climate history of the past 2 million years, the team of experts in climate modeling, anthropology and ecology was able to determine under which environmental conditions archaic humans likely lived.

The impact of climate change on human evolution has long been suspected, but has been difficult to demonstrate due to the paucity of climate records near human fossil-bearing sites. To bypass this problem, the team instead investigated what the climate in their computer simulation was like at the times and places humans lived, according to the archeological record. This revealed the preferred environmental conditions of different groups of hominins[1]. From there, the team looked for all the places and times those conditions occurred in the model, creating time-evolving maps of potential hominin habitats.

"Even though different groups of archaic humans preferred different climatic environments, their habitats all responded to climate shifts caused by astronomical changes in earth's axis wobble, tilt, and orbital eccentricity with timescales ranging from 21 to 400 thousand years," said Axel Timmermann, lead author of the study and Director of the IBS Center for Climate Physics (ICCP) at Pusan National University in South Korea.

To test the robustness of the link between climate and human habitats, the scientists repeated their analysis, but with ages of the fossils shuffled like a deck of cards. If the past evolution of climatic variables did not impact where and when humans lived, then both methods would result in the same habitats. However, the researchers found significant differences in the habitat patterns for the three most recent hominin groups (Homo sapiens, Homo neanderthalensis and Homo heidelbergensis) when using the shuffled and the realistic fossil ages. "This result implies that at least during the past 500 thousand years the real sequence of past climate change, including glacial cycles, played a central role in determining where different hominin groups lived and where their remains have been found," said Prof. Timmermann.

"The next question we set out to address was whether the habitats of the different human species overlapped in space and time. Past contact zones provide crucial information on potential species successions and admixture," said Prof. Pasquale Raia from the Università di Napoli Federico II, Naples, Italy, who together with his research team compiled the dataset of human fossils and archeological artefacts used in this study. From the contact zone analysis, the researchers then derived a hominin family tree, according to which Neanderthals and likely Denisovans derived from the Eurasian clade of Homo heidelbergensis around 500-400 thousand years ago, whereas Homo sapiens' roots can be traced back to Southern African populations of late Homo heidelbergensis around 300 thousand years ago.

"Our climate-based reconstruction of hominin lineages is quite similar to recent estimates obtained from either genetic data or the analysis of morphological differences in human fossils, which increases our confidence in the results," remarks Dr. Jiaoyang Ruan, co-author of the study and postdoctoral research fellow at the IBS Center for Climate Physics.

The new study was made possible by using one of South Korea's fastest supercomputers named Aleph. Located at the headquarters of the Institute for Basic Science in Daejeon, Aleph ran non-stop for over 6 months to complete the longest comprehensive climate model simulation to date. "The model generated 500 Terabytes of data, enough to fill up several hundred hard disks," said Dr. Kyung-Sook Yun, a researcher at the IBS Center for Climate Physics who conducted the experiments. "It is the first continuous simulation with a state-of-the-art climate model that covers earth's environmental history of the last 2 million years, representing climate responses to the waxing and waning of ice-sheets, changes in past greenhouse gas concentrations, as well as the marked transition in the frequency of glacial cycles around 1 million years ago," adds Dr. Yun.

"So far, the paleoanthropological community has not utilized the full potential of such continuous paleoclimate model simulations. Our study clearly illustrates the value of well-validated climate models to address fundamental questions on our human origins," says Prof. Christoph Zollikofer from the University of Zurich, Switzerland and co-author of the study.

Going beyond the question of early human habitats, and times and places of human species' origins, the research team further addressed how humans may have adapted to varying food resources over the past 2 million years. "When we looked at the data for the five major hominin groups, we discovered an interesting pattern. Early African hominins around 2-1 million years ago preferred stable climatic conditions. This constrained them to relatively narrow habitable corridors. Following a major climatic transition about 800 thousand year ago, a group known under the umbrella term Homo heidelbergensis adapted to a much wider range of available food resources, which enabled them to become global wanderers, reaching remote regions in Europe and eastern Asia," said Elke Zeller, PhD student at Pusan National University and co-author of the study.

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