by Whit Gibbons

August 4, 2013

If anything can be considered a driving force in ecology, it is the weather. The following questions are representative of several I've received in the last month.

Q: Much of the southeastern United States has had more rainfall this summer than normal, and weather reports for the Southwest, Midwest and Northeast blab on about how hot it is or how much flooding there is. Considering that a year ago we were talking about the extended drought everywhere, what exactly is "normal"?

Has the record-breaking spring and summer rainfall in many parts of the South had any negative impacts on wildlife - either plants, animals or both? Are the reports of greater numbers of snakes, alligators and mosquitoes real?

A: "Everybody talks about the weather but nobody does anything about it." That's as true now as it was at the turn of the 20th century when Charles Dudley Warner (or possibly Mark Twain) first said it. Weather in most parts of the world is notorious for being unpredictable, and people (including weather forecasters) are going to talk about what they consider unusual.

Twain (or maybe Warner) also said, "Climate is what we expect; weather is what we get."

Thus, "normal" weather for a region or a season changes slightly each year. Actually, having weather that was the same as last year is unusual. The average temperatures, rainfall, wind speeds, etc. all vary from year to year. This natural phenomenon of fluctuating annual weather patterns is one reason climate change models are so difficult for some people to comprehend.

Native wildlife can adjust and adapt to whatever natural weather conditions occur. Extended periods of rain, drought, cold or heat, which vary independent of each other from year to year, are quite natural. No matter what the prevailing weather is over several weeks or months, even from one year to the next, some species will be winners and some will be losers. That has been the natural pattern of species survival for millions of years. The species that are here today had ancestors that successfully weathered the variability and extremes in temperature and rainfall of the region they lived in. That's one of the wonders of evolution.

Much of the Southeast began experiencing an overabundance of rain starting in early summer, but such weather is in no way unprecedented. Therefore, although a few individual organisms may perish, virtually all species of plants and animals - native, invasive or exotic - will persist. A species may be extirpated locally or even over a wide region due to extreme weather. But except in the very rarest of situations, the species itself will continue to exist somewhere. The problems created by various man-made environmental impacts are much greater and have a far more lasting effect than those caused by any natural regional weather conditions.

Some species become more apparent when unseasonably cloudy, rainy and cooler weather occurs during a southern summer. For example, summer breeding frogs might well be more active during such conditions, which can lead to greater activity by animals that eat frogs and tadpoles. Snakes in particular are more likely to be seen on quests for food. Meanwhile, mosquitoes become more abundant during rainy periods in summer. The upside is that insect-eating bats and dragonflies, as well as fish that eat the aquatic larvae, will prosper because of an increased food supply.

The growth of certain grasses and shrubs can also be stimulated by wetter conditions, which in turn might lead to an increase in herbivores such as deer or rabbits. Or various rodents such as rats and mice may become more obvious in areas where they might not usually be seen. Again, more food for certain snakes. And alligators, in areas where they occur naturally, are more likely to be encountered because they tend to move overland during humid weather.

Natural fluctuations in weather are, well, natural. And barring human-caused environmental complications, native species will adjust to such variations, just as their ancestors did before them.

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