Four types of pollution damage forests: acid rain, other air pollution, ozone, and runoff containing excess nitrogen fertilizers. Acid rain consists of industrial emissions containing sulfur dioxides and nitrogen oxides from fossil fuel combustion. In addition to rain, fog, snow, smog, dirt, dust, and smoke carry these compounds; all of these materials can be grouped into the general category of acid rain. Acid rain harms leaves and also makes soils more acidic. Acidic soils display different chemistry than normal soils and this affects nutrient uptake by roots. Acidification of soil also leads to a leaching of nutrients with rainwater. As a result, areas in the soil undergo eutrophication, which is the depletion of oxygen by microbes due to a sudden influx of nutrients, often nitrogen or phosphorus compounds.
Particles carried in smoke and smog change ecosystems indirectly by decreasing rainfall, and they may injure lichens, mosses, and insects in particular. The meteorologist Daniel Rosenfeld of the Hebrew University of Jerusalem explained the process to Cable News Network in 2000: “The smoke and pollution particles, when going into the clouds, distribute water into many small droplets. They are so small that they are very slow in combining into raindrops and other icy precipitation particles.” The consequence is lowered rainfall or even drought.
Trees behave in the same way as humans when they become vulnerable due to aging, poor nutrient supply, or a stress such as dehydration: They become more susceptible to injury. Climate change makes trees vulnerability to infection in two ways: first, by putting physical stress on trees that increases the likelihood of infection, and second, by expanding the normal range of pests, including invasive species. With global warming, the range of many tree pests and pathogens will grow larger and affect trees that had previously been free of disease. Infection then attacks trees already stressed by environmental changes. Pests have another advantage over trees: They can adapt to changing environmental conditions faster than trees.
A greater proportion of stressed trees also gives invasive plants an opening into the forest habitat. These invaders may be nonnative trees, but they are also likely to be plants, insects, microbes, or animals. Not all invasive species kill ecosystems, but many do, and these invaders can take over a forest in a matter of days.
Source of Information : Green Technology Conservation Protecting Our Plant Resources