Close to the edge

A bird flies over a field in Ghana, devouring the insects, which, in turn, are looking to devour the crops. A microorganism munches away at the soil around a tree’s roots on an old sheep pasture in Wales. A tapir wanders the Amazonian rainforest, picking at fruit and spreading seeds far and wide in its droppings. Every single one of these tiny processes matters: to grow crops, to keep the climate stable, to allow all life on the planet to flourish.

But that very biodiversity – which plays such a vital part in the complex ecosystems that keep us and our planet alive – is collapsing. The numbers are staggering: a million of the Earth’s estimated eight to nine million species face extinction; in the sea, 90 per cent of global fish stocks are fully exploited, over-exploited or depleted; and 75 per cent of the Earth’s land surface has been significantly altered by human actions – leaving many species with nowhere to go.

“The cumulative diversity we stand to lose is greater than the age of the universe,” says Dr Rikki Gumbs (PhD Life Sciences 2020), Postdoctoral Research Scientist at ZSL’s EDGE of Extinction programme – that’s EDGE as in Evolutionarily Distinct and Globally Endangered. “The magnitude of the loss we face is terrifying.”

Humans are causing this – we’re currently using the equivalent of 1.6 Earths to maintain the way we live now. So, can humans repair the damage they’ve done? Yes, say biodiversity experts, all hope is not lost – but only if we act now, and act wisely. The great extinction has many causes, so it’s going to have many solutions.

Finding out what birds in Ghana are eating, for example, could lead to practical, effective solutions to biodiversity loss. That’s the aim of Dr Joseph Tobias’s lab, which has pioneered the use of meta barcoding: catching birds and mammals, collecting faecal samples, and sequencing the DNA of all the things they have eaten. “Over time, we build a trophic web from this information: which animals are eating which pests?” says Tobias, Reader in Biodiversity and Ecosystems at Silwood Park, Imperial’s international centre for research and teaching in ecology, evolution and conservation.

Working closely with local communities, they now have information about several hundred birds and bats living on the edge of agricultural landscapes in Ghana and Zambia, and are expanding that research to other tropical regions.

“And that means we can start asking questions about which parts of biodiversity are the most important for humans,” says Tobias. “Which agricultural practices can help to promote nature-based solutions for controlling pest populations, pollinating crops or maintaining adjacent rainforest?”

A world away, in central Wales, Dr Bonnie Waring, Senior Lecturer in Ecology at the Grantham Institute, is working on just such a solution – attempting to turn sheep pasture that has been grazed for centuries into biodiversity-rich forest. Since 2000, around 437 million hectares of tree cover have been lost globally, mainly to agriculture, logging and wildfires. The changing use of sea or land was identified by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Service as one of the five direct drivers of biodiversity loss. And, of course, forest photosynthesis and forest breathing are also vital for removing and returning vast amounts of carbon to the atmosphere. While Waring emphasises that forests should ideally be allowed to regenerate naturally, “sometimes nature needs a helping hand”.

That helping hand could be as simple as a few handfuls of soil. At the sheep pasture where Waring is running her research project in collaboration with charity The Carbon Community, no natural regeneration has been observed. “So, we need to plant trees. But we must help the forest through that very vulnerable early stage of its development where the seedlings are defenceless and very prone to dying of drought or being eaten. And we need to do that by working with the natural ecology of the ecosystem, not against it.”

Just like the gut microbiomes that help us to digest food, trees have evolved over hundreds of millions of years to partner with beneficial microbes that help them acquire nutrients. Waring’s team planted trees and inoculated them with microbes from a very closely located healthy forest. Adding that little bit of soil from a healthy nearby forest made those seedlings grow more than 50 per cent faster.

Waring and her team don’t yet know how this will translate to greater carbon capture and the ecosystem in the long term. But it has certainly speeded up the trajectory of healthy tree growth – and it can be easily replicated by anyone, anywhere, with a little guidance. “Reforestation as a climate solution will not work unless the people who live most closely and interact most frequently with the forests that are created have an incentive to keep those forests,” says Waring. “We can’t have a one-size-fits-all approach. We need adaptable solutions with a low barrier to entry and which can be used by local groups, not imposed across the world by big organisations. This is something else in the toolkit.”

And these tools range from low-tech soil to high-tech data crunching. Dr Will Pearse (MSc Life Sciences 2009), Senior Lecturer in Applied Ecology at the Silwood Park campus, is using the evolutionary history of numerous species to better understand the challenges that face them today. Using fossil records along with DNA sequencing, they build models of how tiny changes in DNA have accumulated through time, and how those changes came together in the ancestors of each individual.

“This allows us to figure out the path that links every species,” says Pearse. “What we lack is a map of how biodiversity change will affect ecosystem functions around the world. We’re building a new generation of forecast models that are capable of forecasting how ecosystems will function after these profound biodiversity declines worldwide.”

A recent project examined two traits of the rodent family tree – body mass and global location – and crunched vast amounts of data looking for patterns. “We found that in two groups of similar-sized rodents that don’t live near each other, body mass evolved more slowly,” explains Pearse. “If you’re the same-size rodent, you eat the same kinds of things and you live in the same kinds of places. You don’t want to live next to someone who is the same size as you, as you’ll be competing for food.”

This has important conservation implications, he says: it’s now understood that trying to move or evolve to avoid competition is a key factor in how a species might behave under pressure, such as climate change. “And tracking how a species we know well is responding to land-use change or climate helps us predict what will happen to those rare and threatened species that are also responding to those drivers.”

Identifying these rare species deemed as highest priority for conservation action is the role of ZSL’s Gumbs. “Pangolins or elephants seem weird because they are alone and unique on the tree of life,” he says. “We measure how evolutionarily isolated or unique a species is and combine that with its extinction risk.” Once a species is identified, a local EDGE Fellow is assigned to it: they learn more about it, and work to help preserve it in partnership with local communities.

This approach often leads to the identification of specific and distinct species, but why is it so important to preserve, say, the Australian mountain pygmy possum or the Archey’s frog? Because we know very little about them, says Gumbs. “We know what the impact would be if we lose bumblebees or worms. But there is a relationship between the distinctiveness of a species and the uniqueness of its features and traits. We are constantly discovering that unexpected species have unexpected benefits.” Consider, for example, the Tasmanian Devil: proteins in its milk were found to kill antibiotic resistant human pathogens. Or the tapir, which has been shown to be extraordinarily good at spreading seeds in its droppings – thus aiding reforestation.