Thursday, 22 July 2010

Rain Rain Go Away, Plant a Pine and Wait A Day (or Two)


Today's Sydney Morning Herald told us that a study from the US had shown that if flowering plants were replaced by non-flowering plants, there would be less rain.

Intriguing. I was curious to chase this one up. Firstly I assume that 'non-flowering plants' are things like pine trees (conifers) rather than say mosses (bryophytes) or even algae...

The story comes from an paper published by Keven Boyce and Jung-Eun Lee at the University of Chicago, published in the latest Proceedings of the Royal Society B (Biological Sciences).

And yes, it's a big rap for the 'angiosperms', the flowering plants. Plants with flowers are the very best plants at moving water from the soil to the atmosphere (transpiration). Not of course because they produce flowers but because of their overall architecture and design.

Most angiosperms have lots of veins in their leaves. These veins, sometimes called 'nerves', are like a metro system in the leaf, carrying sugars one way and water the other, just below the leaf surface.

Boyce and colleagues have published on this topic before, arguing that you can track a fourfold increase in the density of veins in modern angiosperms compared with their ancestors (presumably conifers, cycads, ferns and the like - algae don't have veins, at least not the same kind...).

This latest paper used computer modelling to test how angiosperms contribute to high rainfall in the tropics. They found that replacing flowers - well,  flowering plants - with other kinds of plants, would lead to a 'drier and more seasonal Amazon basin, decreasing the overall area of ever-wet rainforest by 80 per cent'.

They then extrapolate further to suggest that because the diversity of life in the tropics is due to the rainfall and rainforests, the influence of angiosperms on climate has promoted the diversification of not only themselves (i.e. lots of different kinds of flowers) but also insects, other animals and a variety of other plants and critters. These powerful beings (the flowers and their plants) may also have had a role in mass extinctions in the past due to their unparalleled influence on climate.

Heady stuff. So flowers are not only pretty and a good way for plants to reproduce, they have led to the evolution of one of Earth's most powerful overlords, the angiosperm kingdom. I'm sure algae are just as important but you'll have to wait until I find the appropriate scientific paper to back up my hunch.

Image: Not that I'm sore about it, but this is Willare Bridge in the Kimberley, during my recent holiday in the 'dry season'.

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