Just give them a lift

16 01 2009

TvyamNb-BivtNwcoxtkc5xGBuGkIMh_nj4UJHQKupCdpgnnqXqJ70oP0iCjWicCL0ROBPry44AuNOne of the main problems in a rapidly changing world, whether that change arises from habitat loss, invasive species or climate change, is that often the pace of change is simply too fast for many species to keep up. History (both ‘deep-time’ and contemporary evidence) tells us this fact very clearly in the record of extinctions – species that have ‘slow’ life histories (i.e., those that mature late in their lives, produce few young and breed infrequently) are the most susceptible to extinction. More often than not, these tend to be the big organisms because the pace of life scales to body size nonlinearly (the so-called allometry of vital rates). The problem extends to evolution – when the pace of change happens faster than mutation and subsequent natural selection, you are unable to ‘evolve’ to the new environmental state fast enough. The end result – extinction.

So, can we help? Well, it’s fairly difficult to alter reproductive rates unless you do some assisted breeding programme (which generally don’t do much for the conservation status of a species) and you can’t really alter age at maturity or growth rates. You can stop or reverse habitat destruction, and you can translocate species in some circumstances.

So, in the case of climate change, if local conditions become too unbearable for a species (temperature, salinity, precipitation, etc.), just give them a lift to another spot where the new conditions suit! Sounds simple, but it could be rather difficult.

A relatively new Policy Forum piece in Science outlines how ‘assisted colonisation‘ could work for some species. The issues are many – most translocations fail for one reason or another (too few individuals moved, unforeseen predators or competitors, lack of appropriate habitat, etc.), but as we’ve seen the world over in the case of successful alien species, invasions can be remarkably successful (at least from the perspective of the invading species).

The key then is to think very carefully about which species to move and which to leave alone. Of course, generalist, highly adaptable and dispersed species probably don’t need the help, but restricted-range species or habitat specialists could really benefit from such action. You also run the risk of creating more problems than you solve (e.g., new invasive pests, disease introduction). However, a select group of species might just need this very assistance to persist given how much we’ve already change the biosphere, and how much more it will change due to shifting climate in the near future.

It’s controversial, but it could work in many circumstances. That’s why I’m adding this paper (Hoegh-Guldberg et al. – Assisted colonization and rapid climate change) to the Potential list.

CJA Bradshaw

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