Ecologists put controversial biodiversity experiments to the test
Researchers, including scientists from the Senckenberg Biodiversity and Climate Research Centre, have resolved a long-standing question in biodiversity science- whether the positive effects of biodiversity for the functioning of ecosystems are real or an artefact of experimental design? Much of our knowledge of how biodiversity benefits humanity comes from experiments, such as the German ‘Jena Experiment’, which contain combinations of species that are not found in the real world, and this has led some ecologists to question their findings. In the new study the ‘unrealistic’ parts of the experiment were identified and removed, showing that the results are reliable, and giving us greater confidence that biodiversity plays a key role in the Earth’s life support systems, the researchers report today in ‘Nature Ecology & Evolution’.
To most it might not matter much if a handbag is a costly original or an affordable counterfeit, but when it comes to nature imitations could be a whole other matter. Much of what we know about the consequences of biodiversity loss for the ecosystem functions that support life has been gathered from biodiversity experiment sites in which vegetation types of differing plant species richness are created to imitate biodiversity loss. However, the insights gained here have been repeatedly questioned because the design of such experiments includes vegetation types that are rare or non-existent in the real world.
Collaborating with researchers from the German Centre for Integrative Biodiversity Research (iDiv) and the University of Bern, ecologists from the Senckenberg Biodiversity and Climate Research Centre have now put nature’s counterfeits to the test. They compared the vegetation of the two largest and longest-running grassland biodiversity experiments globally with equivalent real-world sites. One of the sites investigated is the ‘Jena Experiment’ in Germany. It was compared to semi-natural grasslands nearby and a large set of scientifically monitored agricultural sites across Germany, known as the ‘Biodiversity Exploratories’.
“We first looked at the sites to see how much they differ in terms of how many species they had, how related they were and what types of functional properties were seen. To our surprise the experimental sites turned out to be much more varied than the real world and to have certain types of vegetation which you would find not in the wild. At the Jena Experiment only 28 per cent of the experimental plots could be considered similar enough to the natural vegetation that we could class them as realistic”, co-author of the study, Dr. Peter Manning, a senior researcher at the Senckenberg Biodiversity and Climate Research Centre, said.
Next, they compared the results of the entire biodiversity experiments to a subset of the experiment that contained only the realistic plots. “Remarkably, the results hardly changed. For ten out of twelve relationships between species richness and ecosystem functioning, the results do not differ significantly between all experiment sites and the subset of only the realistic ones. This suggests that the relationship between biodiversity and ecosystem function seen in these experiments is likely also operating in the more complex real world”, explains Dr. Malte Jochum, lead author of the study from the German Centre for Integrative Biodiversity Research (iDiv) and University of Leipzig.
The authors conclude that their results show the validity of insights about the effects of biodiversity loss gained by investigating biodiversity experiment sites. “In recent years the public has become increasingly aware that biodiversity underpins the Earths life support systems and that its loss threatens humanity. What they might be less aware of is a debate among the scientific community about just how important a role biodiversity plays. By resolving a long running debate these results give us even greater confidence that biodiversity really is a major player, and that conserving it is essential if we are to live well in the future”, says Manning.