Natural and Man-Made Threats to the United States

Natural and Man-Made Threats to the United States

Natural Threats to the United States

Fire

Natural forest fires occur in rainforests, despite their humid nature. Generally, when forest burns in smaller fires, ground vegetation, shrubbery, saplings, and smaller trees are eradicated, while the larger canopy species are spared. The fire has the effect of clearing the forest floor and weaker trees, thus allowing new growth. A forest, stressed by drought or some other factor, is most susceptible to fire, usually sparked by lightening or small human fires that escape neighboring agricultural zones and burn out of control. Research has recently found that over half the Amazon rainforest is at risk of burning during extreme droughts, like the one that struck from July—November in 2005 (Emanuel, 2005).

Drought

Drought affects forests by weakening the system to the point where it is more susceptible to other events like fire and disease. Drought is often partially induced by human activities like deforestation, but it is also a natural occurrence, like El Niño, which periodically causes drought in Asian and American tropical rainforests. El Niño is usually named as one of the influences behind the great Bornean fires of 1982-1983 and 1997-1998. Drought initially weakens canopy plants by reduction of local humidity and rainfall (Franklin, 2006). If the drought is long enough, the leaf litter dries out, killing off decomposers and reducing the effectiveness of nutrient recycling within the system as a whole.

Tropical Storms

Storms can cause extensive damage in the rainforest through tree falls. When a canopy or emergent tree falls, dozens of other neighboring trees, attached by lianas, are brought down with it. Surveying the forest following a storm can reveal numerous tree falls, light gaps, and fallen matter including epiphytes and branches (Hagen, 2012). However, a healthy forest can recover from moderate storm damage in a matter of months or years. The "light gaps" are quickly colonized and soon filled by canopy trees, while the fallen matter is decomposed and reabsorbed back in to the system. Some of the major threats in this regards are highlighted below;

Continued global warming could turn current marginal grasslands into deserts as rainfall patterns change.

Land once incompatible with row-crop agriculture, but which provided a living to ranching families and habitat for prairie wildlife, is being converted to row crops.

Development of urban areas is increasingly cutting into grassland habitat.

Drought-hardy, cold-resistant, and herbicide-tolerant varieties of soybeans, wheat, and corn allow crops to expand into native grassland.

Where only one crop is grown, pests and disease can spread easily, creating the need for potentially toxic pesticides.

Man-Made Threats to the United States

Three in five Americans are most concerned about emergencies involving a natural disaster or terrorist attack, with a health pandemic closely following as a top concern among 46 percent of respondents, according to Federals Signal's 2010 Public Safety survey released today. The survey was done in partnership with Safe America Foundation and Zogby International as part of an effort to uncover Americans' chief concerns and most likely behaviors ...