Animals Shrinking?

Humanity appears to be ushering in new age of minifauna, a kind of Lilliputian world full of runts and dwarves.

At about the size of a five-cent piece, Kugelann's green clock beetle would never be mistaken for a giant. But in the world of European ground beetles, Poecilus kugelanni is no runt. Indeed, some Belgian biologists recently classified the gaudy, green-winged creature as a 'big' beetle.

Big, however, hasn't proved better. Green clock beetle populations have crashed over the past century due to habitat destruction and other threats, and the insect is now endangered in many places. And it's not alone: dozens of Europe's other big-beetle species are also fading away, even as many of their smaller cousins seem to be holding on.

It's a pattern that researchers seem to be seeing everywhere. Around the planet, relatively large species are in big trouble — from lions and tigers and bears to cod, condors, and conifers. Even some heftier snails and salamanders are struggling.

"Size matters," says biologist Chris Darimont of the University of California, Santa Cruz, who notes that the assaults are coming from several angles. On one front, "a larger body size makes a species more vulnerable to all kinds of problems, from getting hunted by humans to habitat change".

One result: Nearly half of the world's large 'megafaunal' mammals — and more than half of the largest marine fish — are now considered vulnerable to imminent extinction.

Meanwhile, overfishing, overhunting, and pollution — and perhaps global warming — are fueling another downsizing trend. These pressures are causing some plants and animals to evolve with astounding rapidity, producing individuals that are on average shorter, thinner and lighter. In other words, they are literally shrinking.

It's a "vastly underappreciated problem," says Darimont, whose own work has shown that a wide range of hunted organisms now have body sizes that have shrunk on average by one-fifth. And human 'superpredators' are causing this shrinkage to occur incredibly rapidly, sometimes in just a few decades — or up to 300 per cent faster than in natural systems.

Together, the trends have some observers wondering whether we're on the verge of a new "age of the minifauna", a kind of Lilliputian world full of runts and dwarves?

It turns out that this is a very old story with a modern twist. More than 25,000 years ago, one megafaunal species — we humans — began to spread rapidly around the globe and in the process helped to wipe out about half of all land mammals weighing more than 44 kilograms.

Link Below:
http://www.abc.net.au/environment/articles/2011/05/09/3208858.htm