[shkkmo]

> if we are going to consider absolute effects on biodiversity, direct human activity has already had a significantly worse effect

Do you have a source for this or are you just basing it on "common sense"

It does toe that Hans have primarily impacted species that tend to sit higher on the food chain. We have caused the extinction of more animals than plants. Rapid warming can kill of plants that can't move quickly migrate quickly enough to stay within the temperature ranges where they can survive.

It isn't just matter of spreading their seeds far enough (like the reforestation of New England), many plants rely on a prexistingnset of conditions created by the the presence of other species to be able to grow. When the required shifts get large enough there simply may not be enough time for those conditions to be established elsewhere before the temperatures in the current areas kills off the species.

Plants species (and animals like coral) serve as a critical component for many other species. It is quite conceivable that rapid global warming will lead to an extinction event that far exceeds anything that humans have managed to date.

Our understanding of ecological systems is still pretty limited and I don't think we can know for sure how bad it will be. I am personally hopeful that we can delevope terraforming techniques to assist with ecosystem relocation that can mitigate some of this.

[ppf]

I don't really have a source on that, although I'm also not aware of any particular species that are known to have been wiped out due to the current climate change. It is, however, fairly obvious that humans have had an enormous impact on pretty much every inhabitable part of the earth. Even without climate change, it's plausible that human activity will ultimately destroy most ecosystems.

>It is quite conceivable that rapid global warming will lead to an extinction event that far exceeds anything that humans have managed to date. >When the required shifts get large enough there simply may not be enough time... >Our understanding of ecological systems is still pretty limited

You've made a number of assertions here about ecology with no reference to research.

This is one of my main issues with the way climate change is presented - much is made of tipping points and the scale of the incoming catastrophe, but the fact is we simply don't know. Even if it is true that we have a low number of decades until irreversible catastrophe, what exactly can be done about that?

[shkkmo]

You are the one who made a strong assertion that the potential for extinction caused by rapid global warming is less than what humans have already caused.

I made relatively few assertions and the ones I did make are basic ecological science. I was pointing out that your strong claim was irresponsible given the plausible possibilities and our limited knowledge.

[ppf]

Not quite. I made the assertion that the ecological damage humans have already caused is much worse than that caused so far by current climate change. We both agree that predicting the further change in climate and its ecological impact is very difficult.

[shkkmo]

> I made the assertion that the ecological damage humans have already caused is much worse than that caused so far by current climate change.

Take a look again at what you are responding too and what you said, it is not at all clear that we're were contrasting past effects on diversity. Indeed, given the topic of the the prospective of rapid global warming causing it is unclear what relevency that point would have.