Tuesday, February 17, 2009

Unintended Consequences

One of the big themes of environmental history is unintended consequences. No matter what we do, nature is going to respond in ways that we don't expect.

However, in the present, is it too much to ask for that people actually think through the consequences of their actions? The case of Macquarie Island is a perfect case in point. Like many islands, Macquarie has been deeply affected by in the introduction of non-native species. Rats and snakes have ripped through native bird and small mammal communities in Hawaii, the Aleutian Islands, and throughout the world. Pigs have had incredible effects as well.

In recent years, scientists and activists have moved to eliminate some non-native species from islands. In general, I think this is a good thing. Islands hold a lot of endemic species. Although many have gone extinct because of human intervention (killing, introducing non-native species, settlement, agriculture), some are trying to hold on. So it seems like it would make a lot of sense to get the cats off Macquarie. The cats were killing the birds. So in 1985, Australian scientists launched a successful program to get rid off them.

The problem is, if you are going to get rid of one non-native species, doesn't it make sense to try and get rid of them all? Or at least all the mammal species? Because with the cats gone, the non-native rabbits took over, denuding the island's plant cover quickly.

“Our findings show that it’s important for scientists to study the whole ecosystem before doing eradication programs,” said Arko Lucieer, a University of Tasmania remote-sensing expert and a co-author of the paper. “There haven’t been a lot of programs that take the entire system into account. You need to go into scenario mode: ‘If we kill this animal, what other consequences are there going to be?’ ”

Well, duh! How do all these programs go through with this simplistic notion of getting rid of one species and not thinking through the ecosystem? This is really incredible. The article discusses many more examples of this as well. Sometimes it is complicated. For some birds such as the Southwestern willow flycatcher, their native habitat has been so destroyed that they actually rely on non-native salt cedar for survival. But in a lot of other cases, a combination of shallow thinking and poor judgement (and quite possibly financial constraints to be fair), have led to disasters like Macquarie. On that island, a new plan is about to be enacted to wipe out rats, mice, and rabbits. Hard to do, but at least the scientists claim to be preparing backup plans in case things don't work out and trying to think through the long-term ecological effects of these changes.