Our ecosystems are declining. Since 1950, we’ve destroyed half of our coral reefs. In the past 300 years, we’ve destroyed 35% of our forests, and of those that have survived, 82% are compromised by human activity.
It’s clear we need to reverse this destruction as soon as possible. But how?
Ecosystem restoration is not merely a matter of planting trees or establishing coral farms, because a forest isn’t just trees any more than a reef is merely coral. Ecosystems are arguably nature’s most impressive feat: interconnected webs of life, in which every single species plays a role.
How do you even begin to restore something so complex?
One answer lies in partnering with ecosystem engineers when undertaking restoration work.
An ecosystem engineer is a species that significantly creates, modifies, maintains or destroys a habitat, with notable examples being beavers, elephants, termites, fungi, coral, trees, kelp, mangroves and oysters. (Read our ecosystem engineer explainer for additional context.)
Humans are ecosystem engineers too and an integral part of nature. We’ve been altering and maintaining landscapes for approximately 60,000 years, after all. But we seem to have lost sight of the fact this work hasn’t been undertaken in isolation. Humans have never been the only ecosystem engineers in an ecosystem. We’ve never worked alone, and there’s a lesson here.
Ecosystem engineers have a critical and profound impact on an ecosystem. Sure, humans can select and replant a range of native vegetation in fragmented landscapes, but this would be time-consuming when you consider Cassowaries eat, digest, poop and spread native seeds for the entirety of their lives. We can manually thin a damaged forest to encourage regrowth, but that’s a lot of labour given elephants do this every day. We can add organic nutrient-rich fertilisers to our soils, but we could also rely on leaf-cutter ants and termites which do this in droves. We can manually restore a wetland, but that would be a huge undertaking, and beavers not only create wetlands but maintain them too. (Here’s a David Attenborough-narrated video of a beaver repair crew for your enjoyment.)
The point is that while humans can undertake restoration work ourselves, this option is often more time-consuming and expensive.
How can human labour compete with that of a species that’s quite literally evolved to engineer an ecosystem? And more importantly, why would we want to? Especially given ecosystem engineers don’t just do the initial work — they do the ongoing maintenance work too.
‘Trophic rewilding’ is defined as “an ecological restoration strategy that uses species introductions to restore top-down trophic interactions and associated trophic cascades to promote self-regulating biodiverse ecosystems”. In other words, an approach where humans lend a helping hand and then let nature do what nature does best.
Why do we need to restore ecosystems?
There are three interconnected reasons why we need to restore our ecosystems as quickly and conscientiously as possible.
First, our health as humans depends on the health of these ecosystems.
Ecosystems provide services that sustain our economies, health and livelihoods — from pollination, erosion prevention and water filtration, to disease management, waste decomposition and air purification. (Read about ecosystem services here.) They’re essential to life on Earth, but when ecosystems are degraded and destroyed, these services slow and halt. It’s only by restoring ecosystems that we can secure these services for our collective benefit.
Second, because we’re truly running out of time.
Many of our ecosystems are getting close to the tipping point after which they’ll no longer be able to cope with environmental change and will shift from one state to another. These shifts are almost always negative. For example, in 2021, scientists revealed the south-eastern section of the Amazon rainforest now emits more carbon than its sequesters. This is the result of deforestation intensifying the dry season, which has changed weather patterns and an increase in fire occurrence. While this is just one section of the rainforest, the Amazon as a whole is fast approaching a tipping point, after which it will begin to transition from a lush tropical forest into a dry, degraded savannah. In addition to being disastrous for the planet, accelerating biodiversity loss and global heating, this will displace the 34 million people who call the Amazon home.
And third, because restoration could help us reach our most ambitious climate and nature targets before it’s too late.
Restoring ecosystems is a climate-change mitigation strategy with huge (arguably overlooked) potential. When healthy, the majority of the planet’s larger ecosystems act as carbon sinks, from tropical forests and wetlands to mangroves, seagrass beds and the ocean in general. In order to minimise the impacts of climate change, we need to go beyond net zero and reach a net negative state. But this will only be possible if we use all the tools at our disposal, and ecosystem engineer-centric restoration is a tool with unmatched potential.
In fact, a recent study in Nature Climate Change shows that reintroducing nine ecosystem engineers — African forest elephants, American bison, fish, grey wolves, musk oxen, sea otters, sharks, whales and wildebeest — would contribute more than 95% of the annual requirement to achieve the global target of extracting 500 billion metric tons of carbon dioxide from the atmosphere by 2100. This in turn would help cap the global temperature rise at less than 1.5° Celsius below pre-industrial levels, as called for in the Paris Agreement.
Yes, you read that right. Nine ecosystem engineers. More than 95% of our annual carbon dioxide extraction requirements.
“There’s a huge untapped potential to consider conserving wild animals as a climate solution,” report lead author Oswald Schmitz, a professor at the Yale School of the Environment, told Mongabay.
“If you do some of the rough calculations, the numbers rival those of what the Intergovernmental Panel on Climate Change is right now promoting in terms of converting everything to solar or wind generation.
“Fortunately, we have the technology to scrub CO2 from the atmosphere. It’s called nature.”
Three critical considerations
When it comes to selecting ecosystem engineers suitable for restoration projects, a study in Functional Ecology shows there are three critical considerations.
First, environmental context. Ecosystem engineers are more impactful when they alleviate harsh environmental conditions in an ecosystem and when their densities are far from saturated.
Second, is ecosystem selection. Projects should focus on ecosystems where ecosystem engineers can most easily establish, are easy to culture and handle, and where scaling up is possible. For example, a beaver dam will have a larger influence if built in a stream of fast-flowing water, as opposed to a pond that already has extensive surrounding wetlands.
Third, not all ecosystem engineers are created equal. In fact, certain ecosystem engineers are so influential they can affect multiple abiotic properties of a system that in turn affect multiple ecosystem functions. These are ‘multi-influence ecosystem engineers’ and they are prime candidates for restoration projects.
Ultimately, the best scenario for ecosystem engineer-centric restoration is when an influential ecosystem engineer already exists in an ecosystem and one only needs to boost its density. These are cases where you just have to get a species over a low-density hump and then positive feedback often takes over for sustaining and promoting the species. For example, oysters need established adults to produce settling cues, and mangroves need enough established adults to help ensure quiescent hydrology for recruitment. Get these two species over these humps, and they’ll exert positive feedback on themselves.
Three case studies
We believe ecosystem engineer-centric restoration is a high-potential, underutilised strategy — and we’re not the only ones. There’s a growing number of active trophic rewilding projects around the world.
Here are three that have caught our eye.
Returning giant tortoise to restore a savannah-like ecosystem
Floreana is the sixth-largest Galápagos island, and used to be home to the Floreana mockingbird, Galapagos racer snake and Floreana giant tortoise. But these native populations were hunted to local extinction by rats, feral cats and other invasive species.
However, a community-led restoration project promises to remove invasive species from the island by 2024 and return 13 native species to the island by 2027.
One of these native species is the Floreana giant tortoise, an ecosystem engineer with the power to reshape the entire island. These tortoises shape ecosystems by selectively grazing on native plants and then dispersing the seeds, as well as trampling and thinning vegetation which creates space for different types of flora to grow.
The return of the giant tortoise will restore Floreana to a savannah-like ecosystem, allowing for the return of other native species. But the benefits won’t stop there. The local Floreana community will benefit from climate resiliency and nature-based tourism, and the ocean will see nutrient cycling from seabirds and reduced sedimentation.
Indeed, restoration projects are more successful when they put ecosystem engineers at the heart, and more so, when local communities and knowledge systems are prioritised as well.
Reintroducing Tasmanian devils to restore and protect forest ecosystems
In New South Wales, Australia, a Tasmanian devil-centric restoration project promises to restore forest ecosystems and make them less vulnerable and more resilient to future fires.
Despite what the name suggests, the Tasmanian Devil roamed mainland Australia until approximately 3,000 years ago, until populations were outcompeted by introduced dingoes, which hunt in packs. But in 2020, 26 devils were reintroduced into a sanctuary in Barrington Tops, New South Wales.
The Tassie devil is a small but mighty ecosystem engineer. As scavengers, they help keep their homes free from disease. By burying leaf litter, they reduce the intensity of wildfires. And as top predators, they push back feral cats and foxes, allowing Australia’s native small mammals to recover. These small mammals in turn enrich soils and disperse seeds as they forage, helping forests regenerate.
Can termites prevent and revert bowalization in Benin?
Numerous studies show that termites are powerful ecosystem engineers, but very little research has been done on their role in ecosystem restoration projects. But a project in Benin, West Africa is filling this knowledge gap.
The northern Benin landscape is suffering from drought and desertification, creating areas of degraded land known as Bowé. These areas have a reduced capacity to retain water, shallow topsoil and low levels of organic matter, silt and nutrients, all of which have negative consequences for the vegetation structure in the area and local communities.
When it comes to solutions, it's not simply a matter of revegetating the landscape. The causes of desertification must be tackled too. This is where termites have the potential to help projects succeed.
Termite mounds help fight off droughts and desertification. The system of tunnels within termite mounds allows water to infiltrate the soil better, and when termites bring plant material to their mounds, it is decomposed by fungi, which changes the soil composition and structure. These effects boost moisture retention and provide nutrients for plants, which increases the likelihood of them surviving and recolonising from the first rainfall following dry periods.
The Mossy team is partnering with Dr. Elie Padonou to run a reversing desertification trial. Together, they’ll plant native tree species that have been found to be especially resilient to drought, and test variables including seed type, water harvesting techniques, termite colonisation and termite introduction.
Nature, people and business — Wedgetail’s three pillars — are all present in this project. By restoring bowé, more grazing space will be available to local herders, and the trees will be a source of food, material and income to boot. In this sense, this project has the potential to meaningfully add to ecosystem engineer-centric restoration as a strategy, while benefiting biodiversity and local livelihoods too.