What do we know about the current state of plant diversity? How is it changing? Why is it changing? And why should we care?
That's a lot of territory to cover in one lecture.
"That's obviously a lot of territory," said evolutionary botanist Peter Crane recently by phone.
But the state of plant diversity comes with the territory when you are former director of the Field Museum of Natural History in Chicago, former director of the Royal Botanic Gardens in Kew, London, and today dean of the School of Forestry and Environmental Studies at Yale. Crane is also a founding board member of the Global Crop Diversity Trust, where he serves alongside executive director Cary Fowler, a native Memphian who was profiled in the Memphis Flyer last year and who was once a student at Rhodes College.
This week, Rhodes welcomes Peter Crane as this year's Phi Beta Kappa Visiting Scholar. Events include meetings with students and tours of the school's arboretum, Overton Park, the Memphis Botanic Garden, and the Dixon Gallery and Gardens.
Is there a single biggest threat to plant diversity today?
Peter Crane: When you come down to it, one of the biggest, one of the most important things is the way we use the land for agriculture and other ecological services. Attached to that is land as habitat. As we fragment habitat, it has implications for the plants that live there. Plants are the basis of the ecosystem, so if the plants aren't doing well, other organisms won't be doing well either.
As we change land use, we often change the ecological processes that sustain those systems — hydrological systems, say. We increase the susceptibility of those systems to, for example, kudzu or to a forest pathogen. We have other impacts: nitrogen and phosphorous pollution from our cars or fertilizers. Some plant species are the equivalent of tigers or rhinos and have become overhunted and susceptible in that way.
How does the U.S. compare to other countries in terms of threatened plant species?
The U.S. is no different from other countries. We're fortunate, though, in that we have land areas set aside in national parks or preserves. But we're doing that in the face of quite severe threats in terms of invasive species and competing pressures, whether it's the use of off-road vehicles on public land or grazing levels.
I think the U.S. is in some respects exemplary, but in other respects, it's got plenty of areas in which to improve.
In the area of large-scale agribusiness, for example?
Agriculture: There's no getting around it, both in the U.S. and the rest of the world. It's a major driver of land-use change. Yet it's quite clear we need that agricultural productivity. We've got 7 billion people to feed, and we need to do it well and thoughtfully. The question is getting the balance right: putting the agriculture where it does the least damage and can be most productive and recognize that we expect other things from our land system, like clean water.
Is there government action in the U.S. you'd like to see right now to improve land use?
Lots of things could be done. Some of these issues will come up as the 2012 Farm Bill is looked at again, including the question of subsidies for various farming practices. The government has been changing its views on biofuels recently, which is helping to take the pressures off. The tax incentives for private land owners to set aside land for conservation easements: Something could be done to improve that.
Aside from government, what can we do on an individual basis?
One thing is to use native species in our gardens in order to move away from high-intensity, highly managed, highly fertilized, highly watered lawns.
We can think about our purchasing — the kind of wood products we use and whether those products come from sustainable sources or not; the kind of paper products we use.
Another obvious area is reducing food waste. Just as the front line in tackling carbon-dioxide emissions must be energy conservation, similar issues apply to food — not wasting food, in order to keep pressure off the ever-increasing amount of land we need for agriculture.
Do you know how many plant species have become extinct over the course of your career?
You can point to species that are only known "in captivity," that are no longer in the wild, the classic North American example being the Franklin tree (Franklinia alatamaha) discovered in Georgia in the 1700s. It's in cultivation now, not in the wild, so far as we know.
It's hard to know if a plant species has gone extinct, but one recent study did show that plants are about as endangered as mammals, maybe not as endangered as amphibians, but more endangered than birds. In the region of 20 percent of the 350,000 plant species are under some kind of extinction threat. That doesn't mean all of them are on their last legs, but they're a conservation concern. That's particularly the case in island systems, where you've got a plant species that grows only in one place.
But we're also discovering new species with very small numbers, such as the Wollemi pine discovered in 1994 near Sydney, Australia. The population is about 100 individuals. They could go extinct through bad luck — a fire, a stray pathogen — but they're an example of a plant brought in for cultivation as a hedge against extinction.
You've worked with Cary Fowler for years.
I know Cary well. He's more important at the Global Crop Diversity Trust than I am. He basically runs it. I've served on the board since the beginning, and it's been a privilege to be associated with it.
In my lecture I'll talk about the trust, which was set up officially for the conservation of plant resources. It's very much focused on our most important crop plants. That covers a few tens of species, but the diversity of plants is on the order of 350,000 species as compared to 10,000 species of birds and 5,000 species of mammals. Many of those plants are crucially important in many ways, not only to us directly but to the ecosystem.
But what do we know about this huge variety of plant life? What's the prognosis? How should we be thinking about the future? Those are also questions I'll be discussing in my lecture.
Final question: You were knighted in 2004. Do I call you "sir"?
Call me Professor Peter Crane, dean of the School of Forestry and Environmental Studies at Yale.
For more information about Peter Crane's lecture at Rhodes on March 1st, go http://www.rhodes.edu/phibetakappa or to Rhodes' Phi Beta Kappa Facebook page at http://tinyurl.com/RhodesPBK. Questions? Contact Scott Newstok at firstname.lastname@example.org.