The value of biodiversity

Research on biodiversity has mostly been performed in small scale controlled experiments. A new study by the Smithsonian Institute and the University of Michigan has researched the effects of biodiversity in the wild. We interviewed Emmett Duffy, the lead author of the study.

Can you tell us how the study on the effects of biodiversity on real world ecosystems was performed?

We searched for all the scientific studies we could find that measured productivity of a natural ecosystem along with the number of species present and environmental factors like temperature and rainfall. Then we used statistical methods to separate and compare the contributions of diversity and environmental factors to productivity.

Did you look at productivity only or also at other ecosystem properties?

We focused on biomass production because this is the ecosystem variable that has been most widely measured and because biomass production is central to so many other ecosystem features such as habitat structure, nutrient cycling, and so on.

What were the main conclusions from the study?

The main conclusion is that the diversity of life forms in an ecosystem is just as important as climate and nutrient inputs in determining its productivity. In fact, biodiversity is even more important in wild nature than expected from experiments, which was a big surprise.

Real world ecosystems are very complex so how did you control for other environmental factors in your research?

In the last decade or so, powerful statistical approaches have developed for cutting through the Gordian knot of complexity in wild ecosystems. As the old saying goes, correlation is not causation, meaning that it’s hard to nail down causes definitively without experiments. Still, because the patterns we found are so consistent with previous experiments and with theoretical predictions, we feel pretty confident they are real.

How does the influence of biodiversity on ecosystem productivity compare to other influences like climate and nutrient availability?

The biggest surprise of this study was that biodiversity appeared to affect productivity just as strongly as climate and nutrients, which are widely considered, master drivers of ecosystem processes. We were all blown away by this – it was really unexpected,

What do you consider to be the explanations for this strong relation between biodiversity and productivity of ecosystems?

There are several possibilities, probably all of which are acting in one situation or another. First species can help one another mutualistically, as plants do with pollinators or corals do with their symbiotic algae. These partnerships have a big influence on how ecosystems work. For example, coral reefs would not exist without that relationship. Second, diversity can provide insurance when conditions change, as they are always doing. Having many species in a system can ensure that at least some of them thrive when conditions change, just as a diversified stock portfolio protects investors from market fluctuations.

Is the effect of biodiversity immediate or do you see a growing impact when the timeline is longer?

We were not able to drill down to that level in our analysis because most of the field studies we found did not include a series of measurements through time. But controlled experiments in both land and marine plant communities indeed show that biodiversity has a stronger influence on productivity through time as the community matures.

What do the finding mean for policy makers?

These results confirm what has been suspected from experiments but never proven in nature: that loss of species can strongly reduce nature’s productivity. This could compromise fisheries, timber production, and other resources we depend on just as human population and needs are growing rapidly. In other words, biodiversity is more than just a pretty face. Having healthy, diversified biological communities is central to the productivity and stable functioning of ecosystems that humanity depends on.

This slideshow requires JavaScript.

Photo’s courtesy of Emmett Duffy.