Mirror mirror on the wall, why is biodiversity the fairest service of them all?
Ecosystems are defined by the way plants and animals interact with each other, and with the non-living things around them. All those species do different things, and have different roles in keeping the ecosystem functioning. So having a variety of species helps the ecosystem hedge its bets: if something goes wrong with one species, another one is there to pick up the slack. And that, in a nutshell, is biodiversity.
We may know this, but it’s really hard to measure. Ecosystems have many, many moving parts: interactions between different organisms, interactions between organisms and the environment around them, etc. Modeling these is very difficult, and you can’t just go out and delete a species in real life. So, we can measure services like flood protection and pollination through their effects on human lives, and even calculate how much the ecosystem behind that service is worth in cold, hard, cash.
Measuring biodiversity
We can’t easily turn biodiversity into cash, but we can measure how biodiversity affects ecosystem function. It’s one step away from creating a financial value, but it’s a start.
Which is why we get so excited when someone does exactly that. To narrow down the effects of biodiversity, a team of researchers looked at a set of experiments on grasslands that:
- looked at the same ecosystem over multiple years;
- compared multiple similar areas in different locations (to see whether the same species affected ecosystem functioning differently based on location);
- measured several different (supporting) ecosystem services (to see how different species affected different services); and/or
- tracked man-made, experimental environmental changes (to see how different species affected different services under different conditions… We feel a bit like we’re in Inception, don’t you?)
Still with us? Hang tight, because we’re going down the rabbit hole. This is what they found:
- 84% of all species supported their ecosystem at least once.
- The species needed to produce multiple services in one year were completely different from the species needed to produce one service in multiple years.
- Ecosystems need different species for support, depending on location, yearly conditions, level of environmental change, etc.
- Common species didn’t do all the work; all species were important, including rare ones.
- Some species could have a tiny individual effect, but a massive total effect.
- Some species could have a tiny total effect, but a massive individual effect, on one service or in one situation.
As for what this all means in real life… well, the authors say it best:
Even more species will be needed to maintain ecosystem functioning and services than previously suggested.
That’s because a lot of older studies had only looked at these factors separately. And in the real world, of course, there are no isolated systems.
Supporting humans
This means that we can’t just focus on one type of biodiversity (say, local or regional) at the expense of another. Losing a species in one area but saving it in another may be fine for regional biodiversity, but the first ecosystem might desperately need that species for proper functioning – and tying it back to our theme, to support all the services it provides to humans.
So there you have it. Biodiversity is fiendishly difficult to measure because there are so many variables to test. But when a few brilliant people do manage to measure it, we find out a lot. The more complex – and the closer to real life – the situation, the more species that are suddenly necessary.
And that’s why we say biodiversity is the most critical of all: ecosystems need biodiversity to keep functioning – and to support human life.
Isbell, F. et al. (2011) High plant diversity is needed to maintain ecosystem services. Nature 477(7363).