We have an idea of what makes people healthy: They eat right, they work out, and they don’t get sick very often. But what makes land healthy? To give you an idea, I went to the Allegan State Game Area. It has two pieces of land that — when it comes to health — couldn’t be more different. The first one is a thriving oak savanna. Ben Savoie is a forester for the Barry, Ottawa, and Allegan Conservation districts.
“It just looks like a big open field and it’s called a barrens—and oak pine barrens—but really it’s anything but barren. There’s a lot that’s going on here.”
There are grasses, woody shrubs, and trees.
“Cherrys, oaks, some sassafras. And few and far between large trees. So we can see here there’s a few large oaks.”
The Allegan Conservation District recently got a grant from the Department of Natural Resources to restore almost 200 acres of oak savanna in the State Game Area. Savoie says that’s because they’re an important habitat for many animals — like the endangered Karner blue butterfly.
“It’s a beautiful vibrant blue, small butterfly and it requires wild lupine to feed and that grows most commonly in savannas and barrens.”
But drive about 20 minutes from this spot and you’ll find land that’s downright sickly.
We’re walking in an area that used to be farm land. It’s a sandy field with a dying cherry tree in the middle. If this land were a person, it’d be coughing up a lung.
“Yeah, this has pretty much just one species of grass through here, this looks like it’s just big blue stem.”
“This is sort of like putting all of your investment into one stock. You want to get a diverse stock portfolio so that if one takes a hit, not all of them go down. You still have some sort of stable ground. When you have just one species in one area, if something happens to it, they’re all gone.”
“Something” like the extreme temperature changes and weather events caused by climate change. Now new research shows that biodiversity might be more important than we thought. And that’s not from just one study. Last year, the Smithsonian Institution and the University of Michigan looked at hundreds of studies that compared biodiversity and climate. In about half of them, biodiversity played and equal or greater role in ecosystem health than climate. Casey Godwin is a postdoctoral research associate at the University of Michigan and one of the authors of the study.
“We would think that climate or temperature and nutrients are two of the factors that are most important in controlling the amount of biomass — of living tissue that we see across the planet. But what this study says is the number of different types of species in those ecosystems can be just as important.”
Of course, Godwin says scientists knew that biodiversity was a factor before. But until this study, few researchers had shown how this plays out in the real world — and there the results are a lot more dramatic.
One way scientists might measure the health of a forest, for example, is through biomass — or the weight of all the plants in that forest. Godwin says a lab test might show that a forest with multiple species of trees has 35 percent more biomass than a forest with just one species of tree. In the real world, it’s closer to 65 percent more.
“In these real ecosystems, these species have coexisted and adapted to one another for thousands of years of evolution. And that’s led to communities — sets of species grow together in a location — that are sort of dividing the labor if you will. They are more efficient at capturing the resources and turning those resources into biomass than any one species can by itself.”
Basically they’ve learned to work together over time instead of competing for the same resources. And just like children, a supportive environment makes it easier for plants to grow.
So it’s clear that biodiversity is good for the health of an ecosystem, but what does it do for us? Why should we care if there’s only one kind of tree in a forest? Godwin says, for one thing, a lot of our drugs come from places with high biodiversity. Unfortunately, they’re being destroyed by people.
“Obviously the effect of biodiversity on ecosystem function goes away if we take away all of the biomass by clear-cutting an ecosystem, or burning it, or converting it to another use.”
All the more reason for land managers like Ben Savoie to restore places like this oak savanna.