Shifting climates provide good and bad news

>> Friday, December 21, 2007

Found this on ecoscraps blog

Climate Change Reflected in Hardiness Zone Maps

Woodrow Wilson of the Arbor Day Foundation: What the hardiness zone map clearly shows is that the climate has warmed, certainly since 1990 when the last USDA map was updated.

Kim Kaplan, spokesperson for the USDA, on the climate change reflected on the maps: It’s not the purpose of the map. It’s not good evidence. It’s not a matter of [whether] there is or isn’t climate change; it’s just that this isn’t a good argument.

Good argument or not there have been many instances where gardens in different areas of the U.S. are able to now grow plants that they once were not able to due to warmer climates. And this has been the case since as early as 2003.

Tropical plants like mangoes and orchids are growing in zone 7! This may be a boon to those gardeners but for natural ecosystems, significant warming could have far-reaching, perhaps disastrous, effects. According to recent research, many wild plants and animals are currently showing significant responses to rapid climate change.

A January 2003 paper in the journal Nature analyzed 143 separate studies on how global warming might be affecting the physiology, behavior, and evolution of wild species. Coauthored by scientists from NASA and Stanford University, among others, the paper concludes that consistent temperature-related shifts have already taken place in organisms ranging from mollusks to mammals and from grasses to trees.

These shifts include flowering and leafing out are taking place earlier in the season. Also, animal migration and egg laying is taking place earlier than normal. As more plants extend their growth range poleward and upward in elevation they bring with them their associated insects and diseases. However, don’t count on both beneficial insect and pest insect populations to increase equally. The history of our planet teaches us that during rapid climatic changes in the past, species showed differential movement. In other words, they reacted independently, rather than in unison, to the environmental stress.

Therefore, just because a particular habitat grew harmoniously two zones warmer than where you are doesn’t mean that it will in its new environ. For example, the pollinators needed for those mangoes or kiwis or orchids may not follow them to your area.

Another worry is that a new species introduced outside of its normal growing zone may become invasive where it wasn’t in its home growing zone.

On the flip side, there may be plants that can no longer grow in your hardiness zone. In a study published in the open access journal BMC Evolutionary Biology, researchers show, using mathematical modeling, that the ideal climate for Cyclamen will become increasingly rare and might have totally disappeared by the 2050's. Some species of Cyclamen are adaptable enough and could survive climate change, but many would probably disappear.

The type of plants that have the greatest chance of extinction are those that require hot, dry summers and cool, wet winters.

A common Great Plains prairie plant, the partridge pea (Chamaecrista fasciculata), could face severe reduction in numbers if climate conditions in the Midwest change to the extremes predicted for the next 25 to 35 years, according to a study to be published in the Oct. 5 issue of the journal Science.


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