Stronger Evidence That Global Climate Change Can Reduce The Varie...( e over tens of thousandsof years. Toda...)

e over tens of thousands of years. Today the Earth tilts at 23.5 degrees relative to its plane of orbit, causing the seasons, but tilt has varied from about 22 to 25 degrees in the past due to changing gravitational effects from the other planets. These changes in the Earth's tilt alter the amount of solar radiation reaching Earth at different latitudes.

Cronin and Raymo discovered that orbital cycles of tilt also influence biodiversity: diverse species-rich communities characterize warm interglacial periods like today (high tilt), while diversity drops significantly during glacial periods when global ice sheets expand in size (low tilt).

The mechanisms that cause diversity to change are still unclear but Cronin and Raymo propose that changes in solar radiation initiate a chain reaction that reduces the productivity of surface ocean plankton communities. This in turn leads to less food resources settling through the water to the sea floor, ultimately limiting the species that can survive in the bottom community. During glacial periods, some abyssal species migrate to shallower refuges around the ocean margins, returning to the abyss during the next warm interglacial. Climate changes also altered deep-sea circulation leading to changes in deep-sea nutrients and temperatures. Competitive and predator-prey interactions among species may also be disturbed by limited food resources and changes in bottom water temperatures.

'"/>

Contact: Donovan Kelly
dkelly@usgs.gov
703-648-4459
United States Geological Survey
14-Feb-1997


Page: 1 2
Related biology news :

1. Evidence builds for potential new cancer drug target
2. Evidence for sympatric speciation by host shift in the sea
3. Evidence for the impact of climate change on deep-sea biodiversity
4. Evidence for fat hormone target in brain
5. Evidence of nanobacterial-like structures found in human calcified arteries and cardiac valves
6. Evidence shows the heart has stem cells able to regenerate muscle tissue lost to disease, wear
7. Evidence for orangutan culture
8. Evidence suggests that standard smallpox vaccine offers long-term immunity
9. Evidence that adults stem cells differentiate like embryonic stem cells published in Nature
10. When Shewanella meets goethite: Evidence found of recognition between animate and inanimate objects
11. Evidence links protein damage to Parkinsons