To restore ecosystems, think about thwarting hungry herbivores

Re-establishing plantings of trees, grasses and other vegetation is essential for restoring degraded ecosystems, but a new survey of almost 2,600 restoration projects from nearly every type of ecosystem on Earth finds that most projects fail to recognize and control one of the new plants' chief threats: hungry critters that eat plants.

"While most of the projects took steps to exclude competing plant species, only 10% took steps to control or temporarily exclude herbivores, despite the fact that in the early stages these plants are like lollipops -- irresistible little treats for grazers," said Brian Silliman, Rachel Carson Distinguished Professor of Marine Conservation Biology at Duke University's Nicholas School of the Environment.

By not protecting plants in their early states, conservationists are missing out on great opportunity to significantly speed restoration, improve its outcomes, and lower its costs, he said.

"Our analysis of the surveyed projects shows that introducing predators to keep herbivore populations in check or installing barriers to keep them at bay until plantings become more established and less vulnerable, can increase plant re-growth by 89% on average," said Silliman, who helped conceptualize the study and was one of its coauthors.

Those gains are equal to or greater than the gains realized by excluding competing plant species, the new survey shows.

"This begs the question: Why aren't we doing it more?" he asks.

The new survey was conducted with input from an international team of researchers affiliated with 20 universities and institutions. They published their peer-reviewed findings Nov. 3 in Science.

Qiang He, professor of coastal ecology at Fudan University and a former postdoctoral research associate of Silliman's at Duke, co-led the study with Changlin Xu, a member of He's Coastal Ecology Lab at Fudan.

The survey's findings have far-reaching implications for efforts to restore vegetation at a time of climate change, He said.

"Herbivores' effects were particularly pronounced in regions with higher temperatures and lower precipitation," He noted.

All of which leads to one inescapable conclusion, Silliman said.

"If we want more plants, we have to let more predators in or restore their populations," Silliman said. "Indeed, the decline of large predators, like wolves, lions, and sharks, that normally keep herbivore populations in check, is likely an important indirect cause of high grazing pressures."

"Conventional restoration is slowing our losses, but it's not expanding vegetation in many places, and climate change could make that even more difficult," he said.

Using predators to keep herbivores in check at restored sites is a relatively untapped approach that could help us boost plant diversity and restore ecosystems that are vital to human and environmental health, in less time and at lower costs," Silliman said. "It's like learning a new gardening trick that doubles your yield."

Once a planting is established, the herbivores are essential too, he added. "Plants just need a small break from being eaten to get restarted making ecosystems. Once they establish, herbivores are key to maintaining plant ecosystem diversity and function."

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Natural GM crops: Grasses take evolutionary shortcut by borrowing genes from their neighbors

Grass may transfer genes from their neighbours in the same way genetically modified crops are made, a new study has revealed.

Research, led by the University of Sheffield, is the first to show the frequency at which grasses incorporate DNA from other species into their genomes through a process known as lateral gene transfer.

The stolen genetic secrets give them an evolutionary advantage by allowing them to grow faster, bigger or stronger and adapt to new environments quicker.

Understanding the rate is important to know the potential impact it can have on a plant's evolution and how it adapts to the environment.

Grasses are the most ecologically and economically important group of plants, covering 30% of the earth's terrestrial surface and producing a majority of our food.

The Sheffield team sequenced multiple genomes of a species of tropical grass and determined at different time points in its evolution how many genes were acquired -- giving a rate of accumulation.

It is now thought these transfers are likely to occur in the same way that some genetically modified crops are made.

These findings, published in the journal New Phytologist could inform future work to harness the process to improve crop productivity and make more resilient crops, and have implications on how we view and use controversial GM crops.

Dr. Luke Dunning, Research Fellow from the University of Sheffield's School of Biosciences, and senior author of the research, said: "There are many methods to make GM crops, some which require substantial human intervention and some that don't. Some of these methods that require minimal human intervention could occur naturally and facilitate the transfers we have observed in wild grasses.

"These methods work by contaminating the reproductive process with DNA from a third individual. Our current working hypothesis, and something we plan to test in the near future, is that these same methods are responsible for the gene transfers we document in wild grasses.

"This means, in the near future, controversial genetic modification could be perceived as more of a natural process.

"Currently, these 'natural' reproductive contamination methods are not as efficient in producing GM plants as those that are used routinely, but by further understanding how lateral gene transfer occurs in the wild we may be able to increase the success of this process."

Since Darwin, much of our understanding of evolution has been based on the assumption that genetic information is passed from parents to offspring -- the rule of common descent for plant and animal evolution.

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Capturing carbon in savannas: New research examines role of grasses for controlling climate change

In recent years, the escalating impact of global warming has prompted efforts to reverse troubling trends, often by planting trees to capture and remove carbon dioxide from the atmosphere and store it. New research from a team led by Young Zhou, from the Quinney College of Natural Resources and the Ecology Center, shows that, in addition to trees, humble grasses also play an essential role in capturing carbon -- more important than previously thought.

A recent initiative set its sights on capturing carbon in tropical savannas, an ecosystem characterized by shared space of trees and grasses. The project initiated a tree planting effort (afforestation) to capture carbon dioxide from the air, which resulted in stored carbon in two primary places: the woody biomass of the growing trees, and in soils. While the effectiveness of storing carbon in trees has been well-established in research, how carbon storage functions in soils was not well defined, and Zhou and his colleagues set out to determine the role grasses played in this effort.

The team, which included scientists from Yale University, Lawrence Berkeley National Laboratory, University of Cape Town, Texas A&M, Kruger National Park, Harvard University, and University of Oregon, conducted a comprehensive study investigating the contribution of grasses to carbon content in savannas soils and assessed the potential impact of increasing tree cover in tropical savannas on soil carbon storage. The study was published in the journal Nature Geoscience.

Using the case study conducted in Kruger National Park, South Africa, and data synthesized from tropical savannas worldwide, the research team demonstrated that savanna soils enriched with carbon from grasses exhibited comparatively higher concentrations of carbon. Their findings showed that grasses accounted for over half of the soil carbon content across tropical savannas, including soils directly beneath trees. This underscores the significant role that grasses play in the accumulation of carbon within tropical savannas.

Their findings showed both carbon gains and losses, as tree cover increased across tropical savannas. The most significant variation was observed in savannas receiving higher rainfall, where tree planting is more likely to thrive, as well as in areas with clay soils and savanna sites that had substantial contributions of carbon storage from grasses.

"This underscores the nuanced nature of increasing tree cover on the dynamics of carbon in savanna soils," Zhou said. "On average, the increase in soil carbon storage resulting from the expansion of tree cover across tropical savannas is negligible."

This finding aligns with the team's previous research published in Nature, which demonstrated that increasing tree cover due to fire suppression led to increased carbon storage in woody biomass, but did not affect soil carbon storage.

"Our findings challenge the commonly held assumption that afforestation uniformly boosts soil carbon storage," Zhou said. "However, we have yet to pinpoint the precise factors responsible for the substantial variation observed in the soil carbon storage response to increased tree cover across tropical savannas."

In general, forests primarily store their carbon in the woody trunks and aboveground leaves. In contrast, a significant portion of carbon in grassy ecosystems, such as savannas and grasslands, is stored in the soil, primarily within the extensive root systems of the grasses as well as decaying organic matter. In the context of long-term carbon storage, carbon retained in soils proves to be more reliable, particularly for a vulnerable future marked by warming and increased likelihood of drought and wildfires, he said.

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200,000 years ago, humans preferred to kip cozy

 Researchers in South Africa's Border Cave, a well-known archaeological site perched on a cliff between eSwatini (Swaziland) and KwaZulu-Natal in South Africa, have found evidence that people have been using grass bedding to create comfortable areas for sleeping and working on at least 200,000 years ago.

These beds, consisting of sheaves of grass of the broad-leafed Panicoideae subfamily were placed near the back of the cave on ash layers. The layers of ash was used to protect the people against crawling insects while sleeping. Today, the bedding layers are visually ephemeral traces of silicified grass, but they can be identified using high magnification and chemical characterisation.

The Border Cave study was conducted by a multidisciplinary team from the University of the Witwatersrand, South Africa, the CNRS (University of Bordeaux), and Université Côte d'Azur, France, the Instituto Superior de Estudios Sociales, Tucumán, Argentina, and the Royal Institute for Cultural Heritage, Belgium.

"We speculate that laying grass bedding on ash was a deliberate strategy, not only to create a dirt-free, insulated base for the bedding, but also to repel crawling insects," says Professor Lyn Wadley, principal researcher and lead author.

"Sometimes the ashy foundation of the bedding was a remnant of older grass bedding that had been burned to clean the cave and destroy pests. On other occasions, wood ash from fireplaces was also used as the clean surface for a new bedding layer."

Several cultures have used ash as an insect repellent because insects cannot easily move through fine powder. Ash blocks insects' breathing and biting apparatus, and eventually dehydrates them. Tarchonanthus (camphor bush) remains were identified on the top of the grass from the oldest bedding in the cave. This plant is still used to deter insects in rural parts of East Africa.

"We know that people worked as well as slept on the grass surface because the debris from stone tool manufacture is mixed with the grass remains. Also, many tiny, rounded grains of red and orange ochre were found in the bedding where they may have rubbed off human skin or coloured objects," says Wadley.

Modern hunter-gatherer camps have fires as focal points; people regularly sleep alongside them and perform domestic tasks in social contexts. People at Border Cave also lit fires regularly, as seen by stacked fireplaces throughout the sequence dated between about 200,000 and 38,000 years ago.

"Our research shows that before 200,000 years ago, close to the origin of our species, people could produce fire at will, and they used fire, ash, and medicinal plants to maintain clean, pest-free camps. Such strategies would have had health benefits that advantaged these early communities."

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