Ecologists breaking (unwritten) ecological laws

Andy Jarvis, our man with the global insights, sends this despatch:



ResearchBlogging.org


This article just came out in Science about assisted colonization. ((O. Hoegh-Guldberg, L. Hughes, S. McIntyre, D. B. Lindenmayer, C. Parmesan, H. P. Possingham, C. D. Thomas (2008). ECOLOGY: Assisted Colonization and Rapid Climate Change Science, 321 (5887), 345-346 DOI: 10.1126/science.1157897)) That is the fancy term for moving a population from one place to another. Over the past few years this concept has been gaining ground, especially with the barrage of horror stories about the impacts of climate change on the geographic range of species. The authors propose a decision framework to identify candidate species for translocation (or assisted colonisation as it seems to now be called). The decision framework consists of criteria for threat, feasibility, and cost-benefit. Amazingly, the whole concept of ecological risk is not taken into account in the decision framework. The authors mention it in the text, and sidestep the issue somewhat by saying that these are short distance translocations, but this may not always be the case. With the best of intentions, we’ve had some really great “assisted colonisation” events in the past that have caused ecological disaster. See Australia, Lake Victoria, the Southern US, etc. etc. The list is endless.

Before I go too far, I must step back and state the positive side of this concept. After all, the objective is conservation. Done properly, with sound risk analysis of direct and indirect impacts on ecological communities (and anthropogenic systems, like … errrr… agriculture), assisted colonisation could save species from near certain doom. An innocent way of seeing it is that you are just lending a hand to species who can’t quite migrate as fast as others. If migration rates are lower than the speed of climate change, or a pesky river gets in their way, then ecologists come to the rescue and move you. It’s like helping an old lady across the road.

Avoiding long-distance assisted colonisation is a useful surrogate for “eco-safety” (a new term is born), but I think it is dangerous as many assumptions are being made with that one. Suggested next article: Risk analysis framework for assisted colonisation. Readers get going.

As a side note, and while I am in the mood for inventing new terms, we also need to come up with a name for this kind of conservation. We have in situ, we have ex situ. What would be good for this kind of conservation? Non-situ could well be the case if you don’t assist colonisation, but I can’t think of a good name for populations that are assisted. Anyone fancy a place in the history books by giving this a name? ((I propose neo-situ. Ed.))

One country’s response to the threat of climate change

“We want our farmers to grow several crops, not just one crop. We are encouraging our farmers to go into organic farming using shrubs, leaves, herbal pesticide and no chemicals involved so that we can reduce dependency on costly chemical fertilizers. We should improve our yields through applying modern farming techniques such as irrigation and water harvesting technologies. … Farmers are also being taught to alternate rows of crops that complement each other in drawing nutrients from the soil or carbon from the atmosphere. … We must diversify. We must change the methods of farming. We want to change and to achieve our desired goals in increasing household food security, increasing our yields, increasing our production. Productivity is what matters most.

So, where do you suppose all that is happening? Here.

Nibbles: Chocolate, Africa cubed, Green wall

Climate change and Africa

Image2.gif I haven’t read Climate change and poverty in Africa: mapping hotspots of vulnerability, and nor am I likely to find the time to do so any time soon. But judging from the write-up at Eldis this paper from the African Journal of Agricultural and Resource Economics will be of interest to those who find this sort of thing interesting. The paper “uses a broad-brush analysis at the continental level to identify areas or ‘hotspots’ that are already vulnerable and likely to suffer substantial impacts as a result of climate change.”

The authors conclude that these results argue against large ‘magic bullet’ approaches and favour smaller, better targeted local approaches and interventions. Considerable future work is needed to refine the hotspots analysis and increase the resolution of impact studies, and thus contribute to a better understanding of the issues facing millions of people who depend on natural resources for their livelihood.

I wonder how that squares with other approaches to vulnerability in Africa, like the models of our pal Andy Jarvis and those of David Lobell?

The perils of protected areas

Does it make sense to conserve crop wild relatives in situ? That’s an extreme way of asking the question, I know, but maybe it is worth putting it as starkly as possible. To concentrate minds, let us say. Such musings were triggered (not for the first time) by the latest niche modelling study trying to predict what will happen to species distributions under climate change.

As usual, it’s not good. Working on the California flora, researchers at Berkeley found “that two thirds of … ‘endemics’ could suffer more than an 80% reduction in geographic range by the end of the century.” The average shift in range will be 150 km, and in many cases there will be no overlap between the old and new ranges. Current hotspots of diversity will disappear. That’s in line with studies more focused specifically on crop wild relatives.

However, “[t]he authors [also] identified several ‘climate-change refugia’ scattered around the state. These are places where large numbers of the plants hit the hardest by climate change are projected to relocate and hang on.”

The usual caveats apply. In particular, the exact results for a given species will depend on whether it can migrate and/or adapt fast enough to track changing climates. But let’s think it through. The global strategy for crop wild relatives conservation says we should

Identify globally, and within each region, a small number of priority sites (global = 100, regional = 25) for the establishment of active CWR genetic reserves.

Let’s assume we identify such a site, because of its interesting or high diversity, say. What would really be the best way of conserving the population(s) found there? If migration is fast enough to track climate across the landscape, surely it would be best to conserve the population ex situ, rather than moving the protected area every once in a while.

If migration cannot keep up with climate, there are only two possible outcomes. Either the population dies out, in which case of course ex situ is the only option. On the other hand, if adaptation occurs, and the population persists, the selection pressure is likely to be so strong and so centred on temperature and water availability, that many useful alleles for other non-climate related traits are likely to be winnowed out. Again, you’d probably want to conserve the population ex situ anyway.

So I guess the answer to the question I started out with is a heavily qualified affirmative. Yes, it does make sense to conserve crop wild relatives in situ. BUT. Only if you also do it ex situ, and only if you do it with a view to what distributions are likely to look like in a hundred years’ time. We should all be looking for those “climate change refuges.” But we should also be collecting those crop wild relatives as fast and as completely as possible.