PAPER: Arthropogenic Impact On Wetlands
ABSTRACT
In the past, wetlands have been considered undesirable and useless; and as a result are being drained and developed. They are being deprived of their natural processes due to flood control systems, municipal development and pollution. There are options to appease both conservation goals and human needs. But the bottom line is that there needs to be consideration of wetlands’ delicate ecosystems and added political protection for them.
INTRODUCTION
Wetlands are an integral part of river ecosystems. They absorb flood waters, filtrate and purify them, and are habitat for one third of the endangered species and about 250 species of birds and 118 species of native fish (Dept. Of Interior 1994, Williams 1996, Crane 1994). Wetlands are also dependent on river systems. Any alteration on a river directly affects the adjacent marshes (Williams and Stewart 1996). They are natural regulators of flood water, and are adversely affected by man-made flood control structures (Dept. Of Interior 1994). They withhold the water and slowly re-release it, lessening the impact from droughts (Dept. Of Interior 1994).
Wetlands also provide other valuable resources. Their trees give shelter for migrating birds, tons of invertebrates and wildlife (Campbell 1993). They hold together the marsh with extensive root systems and process carbon dioxide, reducing green house gases (Campbell 1993). As wetlands are drained and their trees are removed to capitalize on the nutrient rich soil, oil and valuable real estate they possess, the hydraulic balance in the wetlands is disturbed, and thus the biota.
Humans often neglect to acknowledge the thousands of years it took to shape these sensitive systems, and carelessly reap the resources they provide without considering the consequences. Louisiana is losing its wetlands by 50 square miles a year (Adler 1990) and the nation has lost over half of its original wetlands. Needless to say, the impact from human activities has been tremendous by pollution, flood control structures, agriculture, industry, and municipal needs—all of which spoil their natural and productive regimes.
RESULTS
WETLAND LOSS
Flood Control
With the floods of 1973 and 1993, it became abundantly clear that the immense property damage and human suffering was an act of man, not just of human nature (Ridgeway 1993). Nature groups such as Mississippi Rivers, Sierra Club, and the EPA have begun challenging upcoming levee projects due to the astounding evidence of their negative impacts on wetlands. Their target is the Army Corps of Engineers.
For thousands of years, the rivers’ natural behavior has evolved special formation to equip flooding. Within the last century, the Corps has altered those formations; and by treating the river as a navigational tool and as something that needs to be contained, it has increased the damage from flooding (Tobin 1996). But despite evidence of this, the Corps still recommends millions of dollars worth of more channel dredging and levee building (Ridgeway 1993).
Flood control levees not only channel the water, creating a faster, more dangerous flow, but restricts freshwater and river sediments from flowing into the adjacent wetlands (Williams and Stewart 1996). These two components are necessary for ecosystem balance and thus survival (Crane 1994). In fact, without the river’s inflow, the wetlands begin to sink below sea level as in some coastal wetlands in Louisiana (Campbell 1993). Without these wetland ecosystems and the biological processes that take place within them, their ability to soak up floods is also destroyed.
The Army Corps of Engineers refuse to pursue natural means of flood control, and persist with channeling and dredging which aggravates flooding (Ridgeway 1993) despite the EPA’s recommendation against levee improvements projects. The Corps’ attitude is shaped by their ignorant assumption that though wetlands may have an impact on small floods and they would only reduce damage from large floods by a few feet (Macilwain 1993). But, taking into account wetlands in their undisturbed state, restoration hydrologist Donald Hey, estimated that the 1993 flood could have fit into 13 million acres of wetlands (Crane 1994).
The Corps was told as far back as 1851 since one of their own engineers concluded that levees were harmful (Ridgeway 1993). On July 12, 1994, the U.S. government was told by the Interagency Flood Plain Management Review Committee not to rely on the Corps as a sole provider for information about flood control (Audubon 1994). The government took this suggestion seriously when given that the flood control structures of 60 years not only did not reduce flood damage but seem to have doubled the economic losses (Tickell 1993).
The government is now hoping to rely less on engineering and more on nature (Macilwain 1993). The U.S. Forestry and Wildlife Service suggests buying flood land and breaching the levees where lives are not at stake (Crane 1994). There is a general agreement that even taking up dykes would improve flood management (Tickell 1993). This would help replenish some of the 4 million acres of wetland lost of all the ten Mississippi river states (Ridgeway 1993).
Agriculture
Besides the overwhelming burden on the Corps to keep channels deepened for navigation, flood control structures are designed to protect croplands as well. And on top of keeping them from flooding, the most devastating effect on wetlands has been the drainage and planting of crops on their nutrient rich soil (Campbell 1993). Agriculture has been the biggest economic motive for wetland depletion and was the incentive behind 87% of the conversions between 1954 and 1974 (Dept. Of Interior 1994). Farmers drain surface water and destroy the original soil composition also resulting in massive soil erosion (Ridgeway 1993, Kollin 1995). And the drainage of wetlands for agriculture is pointless. The crops exhaust the soil of is nutrients and leave a barren wetland (Crisman et al. 1996). This drainage is also a threat to drinking water because traces of pesticides and other contaminants add up to be poisonous (Adler 1990). Additionally, it seems hardly worthwhile to do this since the U.S. has a surplus of agricultural goods that go to waste (Dept. Of Interior 1994).
Urban/Casinos/Industry
Supplying the nation with water is critical in addition to providing safe and affordable housing and wetlands provide the least expensive locations to develop (Dept. Of Interior 1994). Urban growth into wetlands has grown twice than that of other developments (Tobin 1996). The evidence that this growth aggravates flooding has been described previously in terms of levees and drainage (Tobin 1996). The reason that flooding even poses a problem is due to the fact that there is property there to protect and gets destroyed (Tickell 1993).
Wetlands are also ideal for recreational activities such as marinas and vacation homes (Dept. Of Interior 1994). Yet, the boats are hazardous when inshore because their propellers stir up so much silt that is cuts off sunlight from the algae who supplies the oxygen (Adler 1990). This threatens the wildlife, causes erosion and pollution (Adler 1990).
Other recreational activities have an impact on wetlands as well. On Sept. 21, 1994, it was brought to attention of the Army Corps of Engineers that casinos in wetland areas was detrimental to their biological balance (McCann 1994). It was mandatory that casinos develop on local wetland, and it has been recommended that only the environmentally sound ones remain (McCann 1994).
The oil industry manages to deplete wetlands in a unique way. They drill holes, make routs for trucks, rigs, and canals, which cuts up the root systems of the trees. Then the canals will widen as the water carries away the organic debris (Adler 1990) because it is no longer locked into place by the roots. In some cases on the Louisiana coast line, these routes cause saltwater to come in and destroy the freshwater systems such as what happened in Jean Lafitte National Park in New Orleans (Williams and Stewart 1996). Another crime committed against wetlands, on which GreenPeace did a study, identified industry as the main culprit for putting billions pounds of toxic materials into rivers every year (Adler 1990). Ground water contamination may also be attributed to industry when dangerous metals such as lead and cadmium are soaked up when exposed by mine shafts (International Wildlife 1996).
Forestry
Wetland forests are devastated by industrial intruders but are also victims of the forest industry. The forests are a vital part in wetland survival and it is crucial that they are protected. They serve as a filter system by filtering water as it encounters the root system by taking out nitrogen and phosphorous (Kollin 1995). Deforestation would only lead to excessive erosion which imbalances the system to remove extra nutrients (Crisman et al. 1996). It then just washes into streams and rivers degrading water quality (Kollin 1995).
The timber industry is favor of better maintaining wetlands resources. They drain the surface water to get trucks in and out, but that can have an effect on timber production (Kellison et al. 1994). Some companies have developed a system of periodically flooding old rice farms to regenerate hardwoods to sell (Kellison et al. 1994). But it is also an issue that clear cutting may be a good tool as well. It has been proposed that since clear cutting takes out the shade in an area and makes it easier for sunlight starved species to grow up (Kellison et al. 1994). The evidence is in the case of rice fields where hardwood quickly colonized the site (Kellison et al. 1994). It provides diversity with seedling and sprout reproduction (Kellison et al. 1994). And on the surface this sounds reasonable, but considering that it will easily dry up or maintain biodiversity without canopy, it is better to approach wetlands as complex ecosystems instead of a money making business (Gosselink 1990).
AFFECTS ON BIOTA
Most wetland losses have been due to human activities though natural processes sometimes play a role (Williams and Stewart 1996). In fact, floods have been the most healthy thing for wetland ecosystems, but not for humans (Crane 1994). Flooding washes aquatic organisms into wetlands, allowing them to expand into a new habitat (Crane 1994). And the EPA has stepped in with concern over biotic communities (EPA 1993). The vegetation in an area is determined by the soil and water relationships which encompasses heavy impact by humans (Jahn and Anderson 1986).
Wetlands most important ingredient, second to water, are its vegetation and sandy sediments (Williams and Stewart 1996). The rivers’ regimes have shaped the drainage patterns placing sandy sediments in its adjacent marshes (Williams and Stewart 1996). When this process is blocked, sea level rises and the land sinks to convert from a freshwater wetland to a saltwater marsh (Williams and Stewart 1996). The importance to the biology Is that the wetland acts as a trap creating a very diverse habitat for many species (Jahn and Anderson 1986).
Other important wetland structures to biology is the litter containing woody debris, snags, etc. which primarily house invertebrates, bacteria, and fungi (Gosselink 1990). While these organisms are decomposing biodegradable materials, it is another filtering system (EPA 1993). In addition to the filtering system, trees also provide diversity.
Some of the oldest trees are found in wetlands such as 1,000- 1,700 year old cypress trees (Williams 1996). Then trees affect the algal types depending on the amount of shade they administer onto the water (Kollin 1995).
Trees also affect the rate of evaporation from the land. Depending on the depth of residing waters, a variety of macrophytes inhabit them (Jahn and Anderson 1986). These plants filter out nutrients and wastewater chemicals producing oxygen to the water (EPA 1993).
Invertebrates locate abundantly on these plants. And if there is a change in the plant or its invertebrates, the fish fauna is affected as well in terms of their preferred habitat and food source (Jahn and Anderson 1986). For instance, fish find refuge in floating plants from various predators. But nonindiginous plants like water hyacinths are considered pests and are poisoned by herbicides, thus threatening the fish’s health (Crisman et al. 1996). Also, Fish species spawn in wetland pools and shallow streams (Kollin 1995). The shallow areas are used by carp and ducks to feed on submerged vegetation and reproduction (Jahn and Anderson 1986).
Overall, the major impact on wetlands, short of depletion, is a shift of biotic community to more opportunistic species (EPA 1993). The addition of nutrients and change in hydraulic conditions may degrade the ecosystems in its value as a distinct habitat as it is turned into a general opportunists’ one (EPA 1993). It is even feared that a “sudden biological collapse” may occur due these drastic changes in habitat as they surpass an indefinable threshold (Crane 1994).
DISCUSSION
WETLANDS AS WASTE WATER TREATMENT
Convincing the public and legislators that wetlands are not only a vat of biodiversity, but that there is indestructive economic interest in them as well. The EPA has presented a series of sewage treatments options within wetlands (EPA 1993) and the goal is to meet both conservation and human needs (Crisman et al. 1996).
These new pollution treatment technologies are not just a matter of dumping wastes into a wetland without further consideration. It is about actively managing the physical, chemical, and biological balance within wetlands as well as filtering pollution (EPA 1993). Wetlands are a means to naturally purify water; they are to use the soil and plants and their microorganisms to extract impurities.
One beneficial tactic treatment by periodically releasing certain amounts contaminated water (EPA 1993). These systems are time consuming and require much research but compare to the cost of man made plants with the extra benefit of conservation (EPA 1993). Most of these systems have also acted as education and recreation facilities while providing habitat for waterfowl (EPA 1993). Wetlands consume water from urban storm water, river water and residential pollution (EPA 1993).
The temperate zone and subtropical Florida have increasingly used these highly managed natural wetland for treating waste water (Crisman et al. 1996). And studies have shown that this has been successful (EPA 1993) though the EPA is concerned that just as in unmanaged wetlands this natural intrusion if waste water into wetlands is going to encourage to that individual wetland’s biota (EPA 1993). The issue of water quality in the U.S. is becoming more critical as the water wastes exceeds the wetlands capability to treat it (Dept. Of Interior 1994). When too many nutrients overload (or underload) the system, the cyclic processes are destroyed (Kollin 1995). For example, too many fertilizers will cause an algal bloom covering the surface of the water depleting the body of oxygen (Kollin 1995). And some wetlands simply are not individually equipped to take on a treatment program (EPA 1993).
MOVEMENTS FOR IMPROVEMENTS
In the past, government policies have actually increased the depletion of wetland being the driving force behind the Corps’ research (Campbell 1993). The most challenging issue among legislators were the delineation of wetlands and currently one-fifth of our nation wetlands are not even covered by laws (Campbell 1993). In fact, H.R. 961 neglects to define the most obvious wetlands (almost half in the nation) as wetlands (Lewis 1996). The Clean Water Act requires many wetlands be protected in order to fulfill its requirements (Lewis 1996). This is progress being made to ensure our water supply and future with the CWA being enforced, society’s gains additional benefit with more effective flood control methods and diverse ecosystem (Lewis 1996). And though this bill (CWA) sounds hopeful, it still neglects to define wetlands in the upper mid-west (National Wildlife 1995).
CONCLUSIONS
Wetlands have potential for serving human needs while maintaining diversity. Though we could be over zealous with wastewater treatment by super saturating the system, it is a possibility as an alternative to current treatment plants. Also wetlands in their natural state may be more effective than man made flood control structures.
With this in mind, it is important to preserve wetlands. Yet the short term gain by stripping them of their vital parts has been out weighing their overall benefits. New definition and policies need to be instated to protect them. More research needs to take place to understand their potential as filters for wastewater so that their load is not exceeded. Progress is being made, but steadfast protection is needed to stop unnecessary depletion.
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