Biological research has repeatedly demonstrated that the relationship between producer and consumer is governed by a law of scale. An international research team has now looked into the possibility of replicating this law of nature in the relationship between the production of plants in an area and the number of large herbivores that browse on them. The study reveals that Africa is the only continent where the scaling law is true.
June 2021 saw the start of the United Nations Decade on Ecosystem Restoration. A total of 115 countries have pledged to restore up to one billion hectares of nature worldwide.
One of the biggest challenges will be restoring historic and prehistoric grazing for large mammals, according to a group of researchers from the University of Aarhus and the University of Sussex. What level of restoration should we aim for? How many large herbivores will we need? And how are we going to coexist with these great animals?
A reference in Africa
Researchers examined current low densities of large herbivores in a scientific paper from the Journal of Applied Ecology. In the article, they calculated a reference for large animals based on the relationship between producer and consumer, i.e. plants and herbivores, in nature reserves in Africa.
They point out that this relationship between producers and consumers applies across ecosystems and biomes implying a close correlation between the biomass produced and the biomass of dependent consumers.
However, after studying the density of large herbivores in nature reserves around the world, researchers could only find such a close correlation on one continent: Africa. On other continents, they found strong evidence of wildlife depletion, even in protected natural areas.
“African ecosystems have a species-rich mammalian fauna and a large biomass of large herbivores that are significantly related to plant productivity,” says Camilla Fløjgaard from the Department of Ecoscience at Aarhus University and group leader of research.
“But we can’t find this pattern on other continents, and in general the biomass of large herbivores is much lower than we would expect given the level of productivity,” she adds.
Far fewer animals in European nature
The survey includes data from protected areas, reserves and several rewilding projects in Europe. The researchers found significant differences, as the biomass of large herbivores in natural areas was less than a tenth of the biomass observed in fenced rewilding areas with restored herbivore fauna.
“It’s sobering that even in many protected areas the numbers of large herbivores are only a fraction of what the areas can actually support,” says Camilla Fløjgaard.
Another lower baseline
In the article, the researchers claim that large herbivores are still being moved, hunted and eradicated, and that there is a widespread perception, even among game managers, that there are many herbivores in the wild, perhaps -be even too much. This perception is not supported by the new study.
Rather, efforts to reduce populations of large herbivores may reflect a shifting baseline.
“Even though large herbivores have roamed the landscape for millions of years, it seems that we have become accustomed to landscapes almost completely devoid of them, and we have come to accept this as the natural state of things” , says Camilla Fløjgaard.
Large animals are ‘troublesome’
In the EU alone, there is a plan to allocate 30% of marine and terrestrial areas for the restoration of natural areas and ecosystems.
“Bringing back large animals is crucial to restoring self-sustaining ecosystems and conserving biodiversity, but it won’t be easy,” says Rasmus Ejrnæs, senior researcher at Aarhus University. He keeps on:
“Big animals are a nuisance, damaging crops, disrupting traffic and generally getting in the way. This will require political commitment and careful physical planning, including fenced reserves.”
