Saturday, August 11, 2012

This Island Earth Part IIIa: Big Guy Bias

Well we here at da' Salad have been debating for some time now about how to wrap up the Island Earth series. A whole new slew of data, articles, and arguments has come to light and evolved in parallel with my thoughts on where this series is going... it could get quite convoluted. But we here are firm believers in the maxim that brevity is the essence of wit and let's keep it simple, stupid. So part III will be split up into several, easily digestible pieces to streamline my argument and make it easier to follow my admittedly twisted logic and hopefully provide a solid argument.

Wait, there is an argument? Well let's just put this out there right now:

Dinosaur megaherbivores, on the whole, were actually a lot more forgiving to their respective vegetative communities than mammalian megaherbivores.


That's right you heard it here first at da' Salad. Those big, honking multi- tonne dinos would have had a comparatively softer effect on plant communities than both modern and fossil herbivorous mammal communities.

How could this be? The dinosaurs were so much bigger, they must have just obliterated any plant within sight...this can't be right.

Well, the thing is, no one has to the best of my knowledge proved the opposite of my theory- that dinosaurs were harsher on plant communities than mammals. It was always, let's just say assumed, that dinosaurs were more destructive than mammals. And this says as much about a social bias against all things big as it does about what happens when you assume something- that you make an ASS out of ME and U!

As I detailed here feral pigs most likely were more devastating to island flora than 1 tonne mammoths and on New Zealand island 11 species of herbivorous moas, some at 250 kg, were most likely less severe on the vegetation than recently introduced cloven hoofed herbivores. We can't always assume large herbivores are more destructive than smaller ones.

Studies on island ecology provide a nice test for looking at the comparative effects of differing herbivores on island flora. And if you notice the thrust of many of my recent articles, such as the  Yemen cloud forests and Laramidia, you will pick up on my extension of the concept of "island" to include not just small bodies of land surrounded by water- but any number of bio-physio barriers separating distinct biomes.

And a cursory look at the continents during the Mesozoic will show that much of what we consider continental land was under water. What we really see are a lot of island-continents. Southeast Asia would be a better proxy for these landmasses than say continental Africa.

Cretaceous globe

And it was on these island-continents that megaherbivorous dinosaurs flourished, lived in balance with their vegetative communities, and grew several orders of magnitude larger than modern continental mammals.

How they did this and the adaptations that allowed them to prosper on "this island earth" will be the subject of future posts. Stay tuned!!!

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