Prior to human arrival, California chaparral was dominated by California sage scrub. Today, only remnants of the once-dominant species remain, as it has been nearly eradicated as a result of urbanization and agriculture, and taking their place are older oaks and surrounding alien grasses. Invasive weeds have overrun the ecosystem. California Chaparral is now home to many rare and endangered species. Destroying chaparral ecosystems and replacing them with invasive weeds cause impacts that go beyond merely a disappearance of visual nature. When native plant species are removed, massive amounts of erosion occur because those native plants once provided important watershed protection through their vegetative cover and deep roots. In addition, since the majority of rainwater now runs off instead of filtering into the soil, there is an immense reduction in underground water.
Additional influences of the human population are the effects resulting from grazing, logging, intensive agriculture, urbanization, dams, and water diversions. The many introduction of exotic plants and animal species also cause competition. By cutting down the trees that act as homes for birds and animals, humans have damaged the California chaparral ecosystems. Human-caused ignitions have also increased the frequency of fires that occur in the ecosystem. This has resulted in a complete eradication of chaparral in some areas and degradation in the remaining areas. When areas are burned, non-native grasses are quick to invade, making it near impossible for chaparral to return and recover. As a result, many sections of what was once healthy chaparral are now occupied by non-native weeds. However, people have benefitted the chaparral in some ways as well by repairing water sources that have previously been damaged by water diversion and domestic animals.
Impact of Excessive Fires
(source: http://www.californiachaparral.com/threatstochaparral.html)
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