Daily the news has articles of global warming and climate change. Whether or not you agree with all the predictions, if the climate does change and get warmer, here are some impacts this trend may have on and in your own garden. Much of this information, and more, can be found at the Boston Area Climate Experiment.
Winters seeming warmer lately? Perhaps this is from the fact that the average annual temperature in the Northeast has increased 1.5 degrees (F) since 1970, at a rate of 0.5 degrees per decade. Depending on the rate of emissions (air pollution) this century, by the end the temperatures could increase from 3.5 to as much as 12.5 degrees on average annually.
The hardiness zone map released last year from the National Arbor Day foundation shows much of the Northeast already a zone warmer. A future USDA updated map may show similar. We may have more need in the north to consider the AHS heat zone maps as well as cold hardiness maps when choosing plants. The bright side for gardeners means more plants we can grow. The downsides to warmer temperatures relate to pests and watering. Increased temperatures could lead to more short- and medium-term droughts. There may be more heat waves in summer and extremes over 100 degrees. By the end of the century, under a low emissions scenario, summers in northern New England may be similar to those now in Pennsylvania, and under a more severe scenario similar to those now in the Carolinas. So the models point to a greater need to water, less water, and hotter temperatures for gardening.
Of course pests currently in the warmer south may make their way north, and those already in the north would reproduce faster in most cases. Already in Alaska, British Columbia and Siberia, defoliating and wood-eating insects have increased with the longer summers recently. Some studies also point to a decrease in natural predators of insect pests with a more highly fluctuating climate as many predict with climate change. New weeds and invasive species to the north are predicted to increase with a warmer climate along with the pests.