You may see signs of global warming in your garden or at your favorite park. Lilacs and honeysuckles are blooming earlier today than in the 1970s, as plants sense that spring is arriving sooner. Apples and grapes are blooming about eight days earlier in the Northeast than a half-century ago, just as spring is starting an average of eight days earlier in Wisconsin than back in 1936. Fully 89 out of 100 plant species studied in Washington, D.C., began blooming an average 4.5 days earlier in 2000 than just three decades earlier. Black locust trees are budding earlier in Ohio -- where, like in a lot of places, the growing season is starting earlier and lasting longer.
You might figure all of this means good things for farmers and your favorite fruits and veggies, but California - the nation's agriculture powerhouse - exemplifies how rising temperatures bring good and bad, and in some places like Africa mainly bad. Some tropical areas are becoming too hot and dry to grow crops, according to University Corporation for Atmospheric Research. (See: tinyurl.com/2npky2)
California grows more than 350 types of crops, including nearly all of the country's almonds, artichokes, kiwis, raisins, persimmons, olives and walnuts.
Yet, "California's cornucopia is predicated on its current climate and its supply and distribution of irrigation water," states a report from the California Climate Change Center. (See: vtinyurl.com/38oozs" target="_new">tinyurl.com/38oozs). On the plus side, frost damage will become less likely and the elevated carbon dioxide will give plants a spurt in growth. On the minus side, more insect pests and weeds are expected, and larger fields will need more water to compensate for the heat. A typical walnut orchard is expected to need an extra 5.7 inches of water.
Less fruit is expected to be produced in California because many fruit and nut trees require a minimum number of "chill hours" (temperatures below 45 degrees) so they can flower. By 2100, adequate winter chill "may be lost for many fruit species," according to the California Climate Change Center report.
Bottom line worldwide: Scientists expect warming temperatures to increase agriculture yields in colder environments, decrease yields in warmer environments and increase insect outbreaks. Heat stress - a very likely occurrence - is expected to reduce yields in warmer regions. Heavy precipitation events, which are very likely to become more common over most areas, stand to damage crops and erode soil. Drought areas are likely to increase, portending crop failure or lower crop yields. (See: www.ipcc.ch/SPM6avr07.pdf).
For more info:
* Want to be a citizen scientist? Project Budburst, a nationwide effort, relies on the public to collect information on when plants flower locally. Go to Budburst.org
* Union of Concerned Scientists' "Agriculture Growing Concern": www.climatechoices.org/impacts_agriculture/
* Climate change and food security: www.ers.usda.gov/publications/aib765/aib765-8.pdf
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