Tropical Biodiversity in the Ice Age

[joshuahedlund]

I’m reading End of the Megafauna and learning about so many fascinating creatures that I wish were still alive.

Anyway, I was surprised to see this map showing how small and discontinuous the tropical rainforests became during the last glacial maximum, because I’ve learned about how human activity in the present is shrinking those forests and threatening biodiversity. Because if all extant species survived the shrinking in the Ice Age(s), why are they threatened by today’s shrinking?

I realize that’s probably an oversimplification, but I wasn’t sure where to go to learn more about the complex realities, so I thought this would be a good place to ask.

Some possibilities that come to mind:

• the shrinkings are not equivalent in size or intensity
• tropical biodiversity was harmed by the Ice Ages but recovered between then and the present
• the map is wrong

[John_Harshman]

My suggestions:

1. Loss of habitat is much faster now than it was during the ice ages. There’s no time for forests to move as they once did in response to climate change and no time for animal species to adapt to changed environments. And the loss of habitat will almost certainly be much more extensive than during the ice ages too.

2. The species that survived the Ice Ages are a sample of those that existed. Though our current set may have survived one challenge, that doesn’t necessarily imply that they were all better suited to survive that challenge than the ones that went extinct. There must have been some role for chance too.