TITLE: Apex predators not a quick fix for restoring ecosystems, 20-year study finds
https://phys.org/news/2024-02-apex-predators-quick-ecosystems-year.html
EXCERPT: Wolves and cougars were wiped out in Yellowstone by the early 1920s. Without apex predators or human hunters to control their population, elk fed on the willows along small streams in Yellowstone's northern range, depleting beavers' food supply and building materials and causing them to abandon the streams in favor of more suitable areas.
Historically, beavers and willows relied on each other to thrive. Flooding caused by beaver dams created favorable soil moisture conditions for willows, and willows provided food and dam-building materials for beavers. Without beaver-engineered flooding, small streams in the northern range cut deeper into the landscape, disconnecting roots of willows from groundwater. Willows never recovered their former height and density.
Following the reintroduction of wolves to the park in 1995, as cougar and grizzly populations were rebounding on their own, the elk population dropped from both predation and hunting by humans along park borders.
However, overall browsing of woody food sources has not declined proportionally. As the number of elk has decreased, bison herds have increased. Yellowstone's carnivores typically don't prey on bison because their large size makes them dangerous.
In 2001, [Colorado State University] ecologists began an experiment to gauge whether the Yellowstone ecosystem would recover due to the restoration of apex predators. They established four study areas in the park's northern range, fenced off eight plots to prevent browsing, and constructed simulated beaver dams in some fenced and non-fenced plots to raise the water table.
They also left control areas unaltered. In 2009, they added 21 more control plots to ensure the results of their experiment were representative of the landscape.
If predators regulated the elk population, preventing them from cutting down willows, the landscape would hypothetically return to its previous state. Instead, the willows remained short on control plots, while the fenced sites with simulated dams showed dramatic recovery.
Willows grew more than three times taller in the fenced, dammed areas than in the control plots, indicating the importance of groundwater access in addition to mitigation of browsing.
By manipulating one factor at a time—browsing and hydrology—at many sites for a long time, the researchers were able to show that carnivores were not causing landscape restoration.
"We learned from the science that it was way more complicated," Cooper said.
"Our result is well supported by ecological theory and empirical results from all over the world," Hobbs added. "Disturbing food webs can cause persistent changes in ecosystems."
TITLE: This coastal ecosystem was degraded and damaged. Then, the otters came in
https://www.zmescience.com/science/news-science/this-coastal-ecosystem-was-degraded-and-damaged-then-the-otters-came-in/
EXCERPTS: First, humans hunted the otters for fur. They wiped out most of the otter population. Then, agriculture and industrialization finished driving out the otters completely. With otters being the apex predators, this changed the dynamics of the entire ecosystem. Crabs — one of the otters’ favorite meals — started multiplying like crazy. The crabs started devouring marsh roots that were keeping bank erosion in check. Slowly but surely, this process started accelerating erosion.
Then, the otters came back in.
Otters need to eat a lot of food to stay warm in the cold water; on frigid days, they need to consume up to 25% of their body weight. So you’d expect the environmental impact to be visible pretty fast — and indeed, it was.
By preying on burrowing crabs, which feed on cordgrass, sea otters indirectly protect this vital plant from overgrazing. Cordgrass is essential for coastal wetlands, contributing significantly to their biomass and acting as a natural barrier against erosion. The study’s findings indicate that areas with a healthy sea otter population witness stronger, more resilient marsh edges, less susceptible to erosion and degradation.
“It would cost millions of dollars for humans to rebuild these creekbanks and restore these marshes,” said Brian Silliman, Rachel Carson Distinguished Professor of Marine Conservation Biology at Duke University’s Nicholas School of the Environment, and Director of Duke RESTORE and Duke Wetland and Coasts Center. “The sea otters are stabilizing them for free in exchange for an all-you-can-eat crab feast.”
Of course, it’s easier to prevent than to treat a problem. The otters are here now and they can prevent most of the subsequent environmental damage — but they can’t reverse what’s already been done.
“The return of the sea otters didn’t reverse the losses, but it did slow them to a point that these systems could restabilize despite all the other pressures they are subject to,” Hughes said. “That suggests this could be a very effective and affordable new tool for our conservation toolkit.”
Even so, this is a remarkable finding that could have profound implications not just in California. The implications of these findings are profound, suggesting that the reintroduction and protection of apex predators like sea otters could be a key strategy in combating coastal wetland erosion and loss.
TITLE: If plants can pick fungi to help fight pests and diseases, it opens a door to greener farming and ecosystem recovery
https://theconversation.com/if-plants-can-pick-fungi-to-help-fight-pests-and-diseases-it-opens-a-door-to-greener-farming-and-ecosystem-recovery-221994
EXCERPTS: Just beneath your feet, an ancient and silent alliance endures. This alliance between plants and arbuscular mycorrhizal (AM) fungi is one of the oldest biological partnerships on Earth.
Going back almost half-a-billion years, this relationship paved the way for plants to make it onto land. These early plants, simple and without the complex root systems of plants today, forged an alliance with fungi. This alliance has been instrumental to the evolution of plant life and has helped shape our ecosystems.
These fungi grow into roots where the plants supply them with the carbon (as sugar and fat) they need to survive. The fungi extend thin root-like threads called mycelia into the soil to make expansive networks that can access nutrients beyond the reach of plant roots.
But these hidden microbes do more than just help plants get nutrients. Plants are constantly dealing with insect pests and diseases, and have done for a long time. To deal with this, they evolved sophisticated defences. AM fungi can dramatically enhance these defences.
So could plants be picking their fungal allies based on their ability to enhance defences against pests and diseases? We recently explored this question and proposed hypotheses around how this could happen. The answer could have huge implications for making agriculture more sustainable.
Considering the benefits AM fungi can provide plants, it’s no surprise there has been a lot of interest in using them in environmental management. Studies show AM fungi can have huge benefits for ecosystem restoration by supporting the establishment of native plant communities. Their importance to ecosystem function makes it clear mycorrhizal fungi should be included in conservation efforts.
In agricultural systems, fungi can increase crop growth, nutrient uptake and yields. These benefits have been a major focus for researchers since the 1950s.
While there is ample evidence of the benefits AM fungi can provide for crops, results in the field are inconsistent. There can be a mismatch between the nutritional needs of the crops and the ability of the fungi that are present or introduced to the soil to meet those needs.
Within the roots of a single plant, numerous fungal species can co-exist, forming complex communities. The species that make up these communities may each offer different capabilities – some are better at defence, while others are better at nutrient uptake. The benefit a plant gets from its fungal partners is, in part, determined by which species are present within its roots.
We can apply AM fungi to the soil but this doesn’t mean these fungi will actually partner up with the plant.
So what determines which fungi gain entry to the roots? Do plants have a say in this? And, if so, how do they choose? These questions have long been on the minds of ecologists and biologists.
At the core of this relationship is a complex exchange system. Plants provide the fungi with carbon they need, and the fungi provide benefits to the plants.
Research has shown a plant will play favourites (at least in some cases) with the fungi. They will partner up and give more carbon to the fungi that provide the most nutrients.
Knowing how plants select fungal allies would pave the way for better-defended crops, reducing the need to apply synthetic pesticides. It would open up exciting possibilities for helping ecosystems recover and thrive.
The possibility that plants can identify and select fungi based on the benefits they derive opens up exciting new frontiers in ecological research. As we explore these underground interactions, we inch closer to harnessing the potential of one of the Earth’s oldest symbioses. It is a reminder of the complex relationships that maintain life on the planet, connections that are as important today as they were 500 million years ago when the first plants reached for the sun above and the fungi below.