As regular readers will have realised, I'm something of a sceptic about most things, and one of the things that I've been pretty sceptical about in the past is wildlife corridors. They sound like a great idea: wild spaces are increasingly fragmented (even here in East Africa), and as that process continues populations of plants and animals within these areas will become increasingly isolated from one another. Isolated and small populations are more likely to go extinct than large, well connected populations for a number of reasons ranging from inbreeding - in small populations you're rather more likely to have to mate with a brother or sister than in a large population, which can have serious genetic costs, to simply the risk of extreme events wiping everything out. So connecting those fragments with corridors along which animals can pass seems like a really good idea. Tiny experiments using micro-ecosystems where no-one cares if you isolate populations or connect them seemed to suggest that there might be something in this idea, and all of a sudden conservation corridors were high on the agenda.
The problem with this idea, is that like rather a lot of conservation, it's a good idea with some theory to support it and even some small-scale experiments, but there's rather little experimental evidence that it works in practice. Sure, if you increase the amount of available habitat whilst connecting one patch to another it's good news - but that's not really the point of a corridor and you might have been better able to spend the money buying the narrow strip of expensive land you want a corridor on purchasing a much larger area of cheaper land elsewhere if the benefit is only from the increased habitat area. What's more, once you've identified an area as a corridor it often means that the surrounding area is implicitly identified as unimportant, and may even exacerbate the problem. A quick google scholar search gives a fairly clear view of the debate: Do Habitat Corridors provide connectivity? Biological Corridors: Form Function and Efficacy. Movement Corridors: Conservation Bargains or Poor Investments? Etc. etc. On the one side there are the sceptics who see huge sums of money being committed to conservation corridors with little evidence to suggest they'll meet the stated objectives. And on the other side there are those who say it's sure to work, and can't be bad even if it doesn't.
So, when I heard from a friend recently that he'd been up on Lewa Downs (Kenya) and had seen their elephant corridor functioning, I was really impressed. This corridor connects My Kenya with Lewa Downs and from there to the rest of the Laikipia plateau. What would have made me extremely sceptical about the project's success was that it involves an underpass beneath a main road that's so small elephants have to pass one by one and large animals have to duck to get through! But, despite all this, they do it: the first animals made the crossing last year only four days after the corridor was completed (and the next day was darted to fit a radio collar - bet he regretted that move!). I'm told now that buffalo and smaller animals are also all making the crossing (though not rhino because they've fitted gates that elephants walk over [how about babies?], buffalo can fit through, but rhino can't - quite a good idea if you want to know where your rhinos are. And at the moment I think that's essential...) That's pretty impressive to me (I'm told there are similar - and even smaller - underpasses in South Africa too), and I'm pleased to hear about it's success. I wonder how much is possible because elephants use such traditional routes all the time - would similar underpasses be possible for the wildebeest of Serengeti under a main road if it ever gets built? I wonder... (I do know it wouldn't be such a lovely place to visit!)
I'll leave it to others to decide if it was the best use of the funds in the first place - I can't find an exact figure anywhere, but the rumours are that the whole corridor cost over $1million. Was a real cost benefit analysis done? I'd love to see it if so!