Sir

Your News story 'Time to sequence the “red and the dead”' (Nature 458, 812–813; 2009) reports on plans to sequence the genomes of endangered and extinct species. Supporters claim that these sequences could help us learn why some species became extinct and provide a scientific argument to warn politicians and the public about which species are endangered, resulting in improved policies. Unfortunately, their claim has several flaws.

Conservation biologists studying a change in genetic diversity over time need many specimens to understand the process of extinction, as you imply. However, a limited set of markers would be adequate for this undertaking, so there is no compelling scientific reason for collecting hundreds of complete genomes.

Although DNA samples may be useful in solving some extinctions attributable to pathogens, genome data would not have helped the now-extinct Chinese river dolphin (Lipotes vexillifer), which needed improved habitat — better water quality and a reduction in fishing and boat traffic. Nor would they have helped the northern white rhinoceros (Ceratotherium simum cottoni), which, now probably already extinct in the wild, needed better protection from poaching.

The wrong policy decisions could be made on the basis of population genetic data if these are ambiguous or uninformative about a species' prospects. Take the case of the mammoth and the bison: based on no evidence for a change in mammoth population size over time and the steep decline in bison over some 20,000 years, it might be inferred that bison was at risk of extinction whereas mammoth was not; the reality was the reverse.

For the global preservation of species, it is much more important to reach a timely understanding of ecological requirements and the effects of invasive species and climate, for example, as well as population parameters that influence responses to harvesting. Otherwise, proposals to sequence “the red and the dead” may quickly be reduced to sequencing just “the dead”.