Challenges Facing Estuaries -
Many different factors can affect the health of watershed habitat. No single factor is responsible. In fact, all human activities in the coastal zone potentially affect these areas, and most problems are heightened by the high human population density along the coast. Issues may include fish and wildlife declines, flooding, invasive species, habitat loss, toxic chemicals, or nutrient overloading to name a few. These problems which cause declines in water quality, living resources, and overall ecosystem health, are the result of the interplay of many factors over time and space.
In the interactive watershed graphic that follows, see how everyday activities in the watershed have the potential to contribute to many of the issues impacting the coastal environment.
These areas of activity within an estuary may potentially contribute to common estuary problems and the key management issues.
Forestry: Clear-cutting has immediate impacts on the decline of wildlife populations in an area. Without riparian vegetation, erosion is likely to increase, carrying bacterial or chemical pollutants and excess sediment. The combination of excess erosion, contamination, and change in the natural water flow can result in degraded water quality and reduced hydrologic function. These, along with the fragmentation of forest habitat, impact fish and wildlife. Sustainable forestry practices can alleviate many of these impacts.
Industrial Development: Despite new, cleaner technologies, industries still often emit organic chemicals, heavy metals, and petroleum products into the environment. This air pollution can be subsequently deposited on land and water and leached into groundwater, degrading water quality. These pollutants can poison fish and wildlife and increase human health risks from swimming in polluted water and eating contaminated fish and shellfish. Economic losses also occur from closed shellfish beds and lost tourism. Permitting programs and continued technological improvements can help lessen these problems.
Agriculture (Crops): Poor farming practices can load waterways with excess nutrients from fertilizers. Pesticides and herbicides applied to crops can contaminate waterways and endanger wildlife. Diversion of natural waterways to irrigate crops and the draining and filling of wetlands to provide new farmland threaten natural habitats. EPA estimates that 54 percent of threats to wetlands are due to agriculture. Many farming best management practices can be used to alleviate these impacts.
Alterations to Natural Water Flow and Shorelines: Natural water systems have been altered with the construction of levees and dams; straightening or channeling of rivers; diversion of water for agriculture, industry, or household uses; filling, dredging, and development in wetlands; and armoring of natural shorelines. The negative effects of these modifications include altered water salinities, impacts on fish and wildlife from lost or altered habitat, blocked passages for spawning fish, and increased coastal land loss (erosion). Due to an extensive levee system that prevents sediments from washing down the Mississippi River, Louisiana loses 1 acre of land every 24 minutes. Comprehensive watershed management plans that include restoration and reclamation activities are helping address this issue in many areas.
Agriculture (Livestock): Increased human health risks from contaminated groundwater and negative impacts on fish, shellfish, and seagrasses can result from poor agricultural practices. Livestock waste can degrade water quality with excess nutrients and bacterial contamination. Grazing in riparian and other wetland areas destroys pollution-filtering plant life. Retention ponds and riparian buffers can significantly reduce these threats.
Shipping: Nonnative, invasive species have entered our estuaries by accidental transport via ship ballast water and plant seeds or shoots in shipped products. Nonnative species can compete with and prey on native species, introduce new diseases to native plants and animals, damage habitats, and reduce biodiversity. Economic impacts from invasive species include damaged infrastructure and reduced fish catches. Shipping also often requires construction and maintenance of navigational channels, which can contribute to loss of habitat and water flow changes. Ballast water regulations can help stem future introductions of nonnative species, and efforts to remove exotics and replant native vegetation are under way in many areas.
Dredging: Dredging of a waterway to increase the depth to allow for larger ship movement can dramatically alter the natural flow regime. This can alter freshwater/saltwater flows and impact the ability of the wetlands to absorb and filter water. Impacts to fish and wildlife include lost or altered habitat, and increased sediment loading and resuspension, which reduce water clarity and quality. The beneficial use of clean dredged material for wetland creation projects is one positive strategy for addressing these impacts.
Urban Development: Conversion of natural areas to developed uses results in loss of terrestrial and wetland habitat. In urban areas, storm water runoff and sewer overflows can contribute toxic chemicals, nutrients, and pathogens to waterways. Natural flow may be altered with levees and other flood protection structures, and straightening or channeling of rivers. These alter estuarine water salinities, impact fish and wildlife, block passages for spawning fish, and increase coastal erosion. Storm water management and growth management plans can help protect the natural resources that enhance quality of life in urban areas.
Residential Development: Indiscriminate development of coastal lands for housing and transportation reduces and degrades available natural habitat. Fertilizers applied to lawns in close proximity to waterways contribute to nutrient pollution. Failing residential septic systems deliver pathogens. Clearing of forests, filling of wetlands, and construction of seawalls associated with new home construction all contribute to habitat loss. Cluster and other sustainable development practices, along with educational information for local officials, can help reduce some of the negative impacts of traditional residential development.
Fishing: Unsustainable fishing practices include overfishing of some species, fishing methods that result in habitat damage, and unnecessary bycatch. The effects of these practices include depletion of fish and shellfish populations, impacts on nontarget species, damage to seafloor habitats, reduced biodiversity, and negative economic impacts on fishing-dependant communities. The National Marine Fisheries Service classified 86 of 279 marine commercial fisheries as ?overfished? in 1997. Fish catch and gear limits are methods used to help sustain healthy fisheries.
Invasive Species: Nonnative, or invasive, species can threaten the natural balance of life in estuaries. Invasive species have entered our estuaries by accidental transport in ship ballast water; accidental transport of plant seeds or shoots; and deliberate introductions for ornamental use. Nonnative species negatively effect estuarine ecosystems by competing with and preying on native species; introducing new diseases to native plants and animals; damaging native habitats; and reducing biodiversity. Economic impacts from invasive species include damaged infrastructure and reduced fish catches. Examples of invasive species now well established in the U.S. are nutria, water hyacinth, brazilian pepper, chinese mitten crabs, and zebra mussels. Management plans at many NEP sites include actions to remove exotics and replant native vegetation.
Document taken directly from this site:
http://www.mobilebaynep.com/PIVOT/water/factors/cf.htm
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