Dwindling population

Lakes that have been acidified cannot support the same variety of life as healthy lakes. As a lake becomes more acidic, crayfish and clam populations are the first to disappear, then various types of fish. Many types of plankton—minute organisms that form the basis of the lake s food chain—are also affected. As fish stocks dwindle, so do populations of loons and other water birds that feed on them. The lakes, however, do not become totally dead. Some life forms actually benefit from the increased acidity. Lake-bottom plants and mosses, for instance, thrive in acid lakes. So do blackfly larvae. 

There is now international concern about the dwindling elephant populations in Africa—their numbers have decreased by 40% over the past decade. This concern has led to bans on the export of ivory from many countries in Africa. However, a few nations still allow ivory to be exported. Thus, to enforce the trade restrictions, the origin of a given piece of ivory must be established. It is hoped that the isotope signature of the ivory can be used for this purpose. ... 

Pheromone traps that mimic pests own signals are useful tools for monitoring insect appearances. They can help you determine when the first pests arrive and when the population dwindles. The directions supplied with specific commercial traps explain how to interpret the population fluctuations. See Phero-... 

When arranging your planting and harvesting schedule, include cultivars that mature earlier or later than your usual crop selections. Pests arrive to find their favorite plant hosts have already been harvested or are not mature enough to produce the fruit on which they feed. Either way, damage to your garden is reduced or eliminated and pest populations dwindle in the absence of the appropriate hosts. 

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