by Whit Gibbons

November 3, 2003

Ecologists are involved in a profession that requires answering questions. Research ecologists address questions of how the world works. Ecologists who are college teachers answer questions asked by students. And some ecologists today need to be able to answer questions asked by the general public, the taxpayers who support research and universities. As career training, my University of Georgia graduate students occasionally try their hand at answering environmental questions I receive.

Q: Can you tell me if wildlife has any chance of surviving a wildfire, such as the fires that have destroyed homes and forests in British Columbia and California? Do animals try to escape the fire or are they paralyzed with fright? Do they succumb to the lack of oxygen that results from the fire? Do smaller animals try to burrow underground or is that area too hot? I am not being morbid, I just care about them.

Answer by J. D. Willson (Institute of Ecology): "Humans have come to view wildfire as a bad or destructive event, most likely as a result of our attachment to material objects (e.g., our homes). Certainly, when wildfire burns an area, some wildlife will die, but it is important to keep in mind that fire is a natural part of many (maybe even most) terrestrial ecosystems. While fire may kill a few individual animals, it is often beneficial to animal and plant populations in an area. Fire frees up nutrients, often resulting in an abundance of new plant growth in subsequent years.

"Fire is actually necessary to preserve certain species. For example, redwood trees need fire for their seeds to germinate, and the American prairies would not exist if they were not maintained by the fires and grazing that stop trees from invading. Fire may also be important in controlling insect pests and the spread of disease, and can even produce specific habitats required by some species (such as dead trees for woodpeckers).

"Although some animals certainly die in fires, most escape. Large mammals and birds may outrun or outfly a fire, and most small animals, including mice, lizards, and salamanders, probably take refuge underground. **During a fire, the temperature is not elevated even a few inches beneath the soil. Animals that die are likely weak, old, or sick and probably would have died soon anyway. So, yes, some animals certainly die in fires, but fires, on the whole, probably do more good than harm to animal populations. Some scientists have even suggested that fire suppression by humans has done more damage to animal populations than logging."

Q: I am doing a research paper on mosquitoes in an honor's biology course. How do mosquitoes develop immunity to substances; can they develop immunity to pesticides and insecticides?

Answer by Luke Fedewa (Institute of Ecology): "Generally, animals (including mosquitoes) within populations will have a range of tolerance to pesticides and other environmental entities, including microbes, toxic metals, and temperature. Immunity is a term reserved for the physiologic response that fends off pathogens (disease-causing agents that include toxic substances, bacteria, and viruses). Although, pesticides may stimulate the immune system, they generally interrupt physiologic pathways or damage internal organs in a manner that causes death through bodily dysfunction.

"Since a differential tolerance occurs among individuals within populations (collections of mosquitoes in your case), mosquitoes can adapt their population-level tolerance to certain pesticides, assuming a differential tolerance exists or becomes formed during exposure. For example, let's say I use a pesticide containing a chemical that kills 90% of a mosquito population. The next time I use this chemical it may only kill 80% and the next time only 70%, because a greater proportion of the survivors after each bout are those with immunity. Meanwhile, if they have produced offspring and the immunity has a genetic basis that can be inherited, the parents with immunity are more likely to produce offspring that are immune. The rate of proportional immunity within the population will depend on a number of different characteristics, including but not limited to environmental factors, genetics, and the chemical itself. But the general trend toward immunity can and does occur."

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