By Michael d'Estries on MotherNatureNetwork, mnn.com

New study shows that soil-inhabiting creatures contracted in size by 30-46% during a global warming period millions of years ago.

Beyond the environmental implications of a warmer planet, scientists now believe that increases in carbon dioxide levels and temperatures may lead to smaller lifeforms.

A new report published by researchers confirms that 55 million years ago, something very similar happened. During this period, called the Paleocene-Eocene Thermal Maximum, carbon dioxide levels in the atmosphere spiked. Theories for the rise range from volcanic activity to comet impacts to a massive release of methane.

The study found that soil-inhabiting creatures decreased in body size by nearly half in response to atmospheric warming. It was already well known that mammals were reduced by almost 50 percent -- but this new information confirms the effects of global warming on those underground as well.

"The take-home lesson is that there can be cascading effects that ripple through an ecosystem when you change just one aspect," Jon Smith, a scientist at the Kansas Geological Survey, told U.S. News & World Report. "Modern climate change can have many effects that aren't going to be as immediately visible as sea-level change. We could be changing soil conditions over vast portions of the world and affecting the soil organisms themselves--and that will impact our own agriculture."

Along with a decrease in size, the researchers also found shorter lifespans associated with the insects -- distant relatives of modern ants, cicadas, dung beetles, earthworms and crayfish.