07.05.08
More extinctions from global warming
This is an odd one, as reported by Janet Raloff in Science News:
… The new paper focuses on tuatara, somewhat-bizarre lizardlike creatures that exist as remnant populations and only on several uninhabited New Zealand islands. Most of these tiny landmasses amount to little more than sheer, rocky outcroppings no more than 5 hectares (~12 acres) in size. Their wildlife has developed in a fairly stable environment and relative isolation. Indeed, the tuatara are frequently characterized as living fossils for the fact that they’re the sole survivors of one of the four orders of reptiles and are little changed from ancient ancestors.
Among their many oddities, these critters have one of the longest reproductive cycles known, grow slowly, and may live four score years or more. Like many reptiles, their gender is determined by the temperature at which eggs incubate. And they incubate in earthen nests a long time — typically 11 to 14 months.
The warmer that nest, the more likely a hatchling will be a he, not a she. So, if the climate leads to substantial nest warming, there will likely come a time at which every tuatara born will be male. That time could be within this century, hints a paper published today in Proceedings of the Royal Society B, although Nicola J. Mitchell of the University of Western Australia and her colleagues leave fairly vague how soon that critical date might arrive.
Part of the reason: Theirs is a modeling paper. So the authors ran a range of scenarios through their computer program, graphing the projections it spit out. Gauging the most likely projection requires making a lot of assumptions — and hoping that the scientists or their computer model were sophisticated enough to account for the most likely factors that would affect gender. These include: how much the local climate will warm in the near future, whether nests will warm proportionately, whether tuatara will plant their eggs at lower depths to keep them cooler in the future, and whether moms will lay their clutch at the same open sites as the climate changes or instead begin to nest at shaded locales elsewhere on their island. …
Complete article at the link.
