Eight years ago, I helped launch NRDC's BioGems Initiative to protect threatened special natural places throughout the Americas - ranging from the Alaska's Arctic to Chile's Patagonia. We have worked very hard to ensure that these treasured wildlands — and their wildlife — are not destroyed or degraded by dams, timber, mining and other short-sighted developments. Central to every one of our BioGem campaigns has been the engagement of more than 500,000 BioGem Defender e-activists who have sent more than10 million messages. Despite our many victories, it is now clear that all of our BioGems are facing an overriding threat — climate change. Now we hope that our activists and other concerned citizens will take part in 350.org's International Day of Climate Action set for this October 24th.

Recently the international scientific community has reached a consensus that greenhouse gases are warming the planet faster than ever before. Many ecosystems and species are very sensitive to changes in temperatures. Scientists already see that climate change is accelerating the rate of extinction, as species so uniquely attuned to their own environmental conditions cannot adapt rapidly enough to their altered ones.

The warmer temperatures will affect every ecosystem on the planet, whether it flourishes in the depths of the ocean, the dense mountain forests, or a wandering prairie stream. All life will be impacted. Due to increasing temperatures, storm systems will intensify and weather patterns will change, providing for increased pest populations, water stress and the spread of diseases. Warmer, drier conditions and invasive species will undermine the very base of the ecological pyramid: the microorganisms and insects. This often invisible weakening of the food chain jeopardizes the survival of the keystone species we all know and cherish, such as the bear and the jaguar.

The oceans will be no less affected; the seas are already becoming less hospitable as they absorb higher amounts of carbon dioxide from the atmosphere. This process, called ocean acidification, distresses marine species that need specific molecules found in the water to build their shells-animals like plankton and coral. Take a look at NRDC's recent film on the subject — "Acid Test". As more carbon dioxide is absorbed by the ocean and the water grows more acidic, less of these crucial molecules are available and the tiny animals are unable to build strong protective shells. Without these species, the rest of the food web — up to the gray whale and vaquita — is in danger.

While the prospect of climate change in the future remains uncertain, what is clear is that our planet is already experiencing warming conditions. In recent years, researchers have documented the plight of polar bears, which are starving from diminished food sources and from the lack of sea ice, from which they attack their prey. Scientists have also researched the impact of climate change on tropical forest species, such as the Quetzal in Costa Rica's Monteverde Cloud Forest, which is now threatened by new predators forced into the high altitude forest by the warming temperatures below.

We have surveyed these scientific findings and reports about the climate impacts on a range of natural environments and regions. Over the coming days, we will share with you the identified likely and possible effects of climate change on each of NRDC's BioGems. (Thanks to Antonia Sohns of Stanford University and to Amanda Maxwell and my other BioGems colleagues who helped to pull this series together.)

NRDC has made constraining climate change our highest priority. We are working at every level to push for solutions which will reduce greenhouse gas emissions and move us to a greener, more sustainable economy. We hope that all of our BioGem Defenders will join in this fight.

One way you can help save all of our BioGems at once is to join us and 350.org in participating in a global day of action on October 24th, 2009. We are inviting all of our members, e-activists and concerned citizens worldwide to take a photograph incorporating the number 350 in a special place and then upload it to the 350.org website before this Day of Action. Why 350? Some of the world's leading scientists have agreed that 350 parts per million is the concentration of carbon dioxide in the atmosphere that still allows us to moderate climate change. We also urge you to join one of the hundreds of actions around the globe taking place on October 24th. Even if you can't make it to one of our BioGems for a photograph or on the day of action, you can organize or join an action in a special place in your own community. Visit 350.org to explore the actions that are already planned, or to register your own. Please, join this unified call to demand strong climate commitments from global leaders when they meet in Copenhagen in December. Act Now. And act on October 24th. Our BioGems — and we — are running out of time.

Become an NRDC BioGems Defender

Today is Blog Action Day, the largest single social action event on the web; more than 6,900 bloggers have signed up to write about global warming.  NRDC is a partner of today's online event.