Extinction

Stabilization of Carbon Dioxide (3)

See below new policy on comments on this blog.

In the previous two blogs I have been talking about the need for stabilization of carbon dioxide in the atmosphere. Take away messages are that we are committed to warming, that warming will be with us for a long time, and that if we were to reduce our greenhouse gas emissions by 70% or more over the next 100 years, then it would make a difference to the amount of warming that we would see. That is, it is within our wherewithal to make a difference. But, every year that we wait will lead to the accumulation of an additional 9 parts per million (ppm) . So far the discussion has focused on the physical climate system.

There is a growing literature on the impact of global warming on ecosystems. Warming directly impacts the ecosystem, but often the greater impacts to ecosystems are felt through the impact on water availability. If precipitation amounts and patterns remained the same, then increased warming would increase evaporation and, in general, reduce availability of water in the ground for plants and animals. Of course, precipitation amounts and patterns are expected to change, and the situation is far more complex that simply increased water stress. Since ecosystems evolve to be in balance with the availability of nutrients as well as climate, any changes in climate are expected to have related changes in ecosystems. Often these changes would be expected to appear as changes in the ranges of species, perhaps with the appearance of warm and temperate adapted plants and animals at higher latitudes. Another way changes are expected to occur is with spring coming earlier and fall lasting later into the year. (links to previous blogs at the end.)

Another way that ecosystems respond is species extinction. There have been numerous times of mass extinctions in the past, and we are, in fact, in a period of mass extinction today. The figure is from the Millennium Ecosystem Assessment, and it is a summary of extinction rates past, present and future. The past is based on the fossil record, and, for mammals, the historical rate of extinction was on the order of one mammal species for every 1000 mammal species in existence. The current rate of mammal extinctions is 50 to 1000 times that historical rate. This accelerated rate is largely related to humans, the expansion of humans over the globe, and the use of resources by humans and the impact of the waste of humans. Climate change is a part of that mix. Looking into the future, the rate of extinction is expected to increase even more.




Figure 1: Rate of Extinction from the Millennium Ecosystem Assessment.


This week the National Academy of Sciences released a small supplemental publication discussing the impact of climate change on ecosystems. ( Free Ecosystems and Climate Change Document ). This publication serves as a portal to a much more exhaustive study completed last year. The study talks about extinction. One conclusion is that if the planet were to warm at the rates projected in the business as usual scenarios of carbon dioxide increase, then 20-30% of the species that have been studied risk extinction. In some cases this due to stress related to climate change being the last straw for an already stressed species.

One of the major issues of warming and species adaptation or extinction is the speed at which the warming will occur. If carbon dioxide were to make it to 550 ppm or more in the next 100 years, a very likely scenario, then the Earth would see, in a century, changes in the amount of heat held near the surface of the Earth (i.e. the energy budget), that have previously occurred over tens of thousands if not millions of years. And these changes in the past have been associated with vast changes in ecosystems - for the most part, without the presence of humans. The speed at which this warming is expected to occur amplifies the rate of species extinction. It is an obvious conclusion that the same level of carbon dioxide reductions that would have significant impact on the physical climate system, would also help to maintain some of the biodiversity that we currently have. (And yes, the problem of ocean acidification from excess carbon dioxide remains to be addressed.)

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Need for a policy on comments: Many of the recent comment streams have disappointed me. I have received notes from people about how the discussion has degraded, and I have seen this written in the comments on other blog sites. Therefore, I am going to start to manage the comments at some level. Neither I nor WU have the resources to moderate the blog comments. Therefore, the only real tool I have is to ban comments. So I plan to start banning comments from those who I feel are at some level abusing the forum and simply being disruptive. This means streams of comments from the same people that add nothing new and comments which pull an isolated fact or figure out of context and use these as darts just to toss at the climate change dart board. I welcome discussion and discourse, but annoying heckling and obsessive chatter is simply annoying. So I plan to use my power to ban, which I will do for a limited amount of time, with repeated abuse becoming permanent.








Ye Olde Stabilization Blog: A Strange Urgency

Previous Stabilization Blogs:

Warm for a 1000 Years

How Much Warming Can we Avoid

Previous Blogs on Phenology and Ranges of Trees

Series of Blogs in 2008 of Spring Coming Earlier

Trees Moving North