ECOSYSTEM RESTORATION
Humans depend greatly on an ecosystem services. An
eco /or ecological systems or services may be defined as a community of plants
and animals interacting with each other and their abiotic, or natural,
environment. Typically, ecosystems are differentiated on the basis of dominant
vegetation, topography, climate, or some other criteria. Boreal forests, for
example, are characterized by the predominance of coniferous trees; prairies
are characterized by the predominance of grasses; the Arctic tundra is
determined partly by the harsh climatic zone. In most areas of the world, the
human community is an important and often dominant component of the ecosystem.
Ecosystems
include not only natural areas (e.g., forests, lakes, marine coastal systems)
but also human-constructed systems (e.g., urban ecosystems, agro-ecosystems,
impoundments). Human populations are increasingly concentrated in urban
ecosystems, and it is estimated that, by the year 2010, 50 percent of the
world's population will be living in urban areas.
These ecosystem services vary greatly and include such
things as erosion control, water and air purification, food, recreation, a list
that could go on endlessly. To put things into a sharper perspective, at this
point in time, we need ecosystems for our continued survival. There are many
reasons to restore ecosystems, some include :
1.
Restoring natural
capital (i.e. goods and services);
2.
Mitigating climate
change (e.g. through carbon sequestration);
3.
Helping threatened
or endangered species recover, and
4.
Aesthetic reason.
There are also moral reasons to restore ecosystems. Some
would say that we have degraded, and in some cases destroyed, many ecosystems
so it falls on us to ‘fix’ them.
There is also the dissenting opinion that ecosystem
restoration is not a valuable use of our time. Reasons for this opinion can
include :
1.
Restorations are
not economically feasible;
2.
They don’t always
work;
3.
They are expensive
(money could be put to better uses); and that
4.
Ecosystems
naturally change over time and can recover by themselves.
The problem is that we cannot restore an ecosystem to the
exact same state it was in before we disturbed it. This is because, as Anthony
Bradshaw claims, “ecosystems are not static, but in a state of dynamic
equilibrium…. [with restoration] we aim [for a] moving target.”
Even though an ecosystem may not be in its original
state, the functions of the ecosystem (especially ones that provide services to
us) may be more valuable than its configuration. One reason to consider
ecosystem restoration is to mitigate climate change through activities such as
afforestation. Afforestation involves replanting forests, which remove carbon
dioxide from the air. Carbon dioxide is a leading cause of global warming and
capturing it would help alleviate climate change.
ECOSYSTEM HEALTH
It
is important to recognize the inherent difficulties in defining
"health," whether at the level of the individual, population, or
ecosystem. The concept of health is somewhat of an enigma, being easier to
define in its absence (sickness) than in its presence. Perhaps partially for
that reason, ecologists have resisted applying the notion of "health"
to ecosystems. Yet, ecosystems can become dysfunctional, particularly under
chronic stress from human activity. For example, the discharge of nutrients
from sewage, industrial waste, or agricultural runoff into lakes or rivers
affects the normal functioning of the ecosystem, and can result in severe
impairment. Unfortunately, degraded ecosystems are becoming more the rule than
the exception.
The
study of the features of degraded systems, and comparisons with systems that
have not been altered by human activity, makes it possible to identify the
characteristics of healthy ecosystems. Healthy ecosystems may be characterized
not only by the absence of signs of pathology, but also by signs of health,
including measures of vigor (productivity), organization, and resilience.
Vigor
can be assessed in terms of the metabolism (activity and productivity) of the
system. Ecosystems differ greatly in their normal ranges of productivity.
Estuaries are far more productive than open oceans, and marshes have higher
productivity than deserts. Health is not evaluated by applying one standard to
all systems. Organization can be assessed by the structure of the biotic community
that forms an ecosystem and by the nature of the interactions between the
species (both plants and animals). Invariably, healthy ecosystems have more
diversity of biota than ecologically compromised systems. Resilience is the
capacity of an ecosystem to maintain its structure and functions in the face of
natural disturbances. Systems with a history of chronic stress are less likely
to recover from normal perturbations such as drought than those systems that
have been relatively less stressed.
]
Healthy
ecosystems can also be characterized in economic, social, and human health
terms. Healthy ecosystems support a certain level of economic activity. This is
not to say that the ecosystem is necessarily self-sufficient, but rather that
it supports economic productivity to enable the human community to meet
reasonable needs. Inevitably, ecosystem degradation impinges on the long-term
sustainability of the human economy that is associated with it, although in the
short-term this may not be evident, as natural capital (e.g., soils, renewable
resources) may be overexploited and temporarily enhance economic returns.
Similarly, with respect to social well-being, healthy ecosystems provide a
basis for and encourage community integration. Historically, for example, native
Hawaiian groups managed their ecosystem through a well-developed social
cohesiveness that provided a high degree of cooperation in fishing and farming
activity.
Another
reflection of ecosystem health lies directly in the public health domain. In
spring 2000, a deadly strain of the bacterium E-coli (0157:H7) entered
the public water supply in Walkerton, Ontario, Canada, causing seven deaths and
making thousands sick. This small town, with a population of five thousand, is
in a farming community. Inadequate manure management from cattle operations was
the likely source of this tragedy.
HOW HEALTHY ECOSYSTEMS BECOME PATHOLOGICAL
Stress
from human activity is a major factor in transforming healthy ecosystems to
sick ecosystems. Chronic stress from human activity differs from natural
disturbances. Natural disturbances (fires, floods, periodic insect
infestations) are part of the dynamics of most ecosystems. These processes help
to "reset" ecosystems by recycling nutrients and clearing space for recolonization
by biota that may be better adapted to changing environments. Thus, natural
perturbations help keep ecosystems healthy. In contrast, chronic and acute
stress on ecosystems resulting from human activity (e.g., construction of large
dams, release of nutrients and toxic substances into the air, water, and land)
generally results in long-term ecological dysfunction.
Five
major sources of human-induced (anthropogenic) stresses have been identified by
D. J. Rapport and A. M. Friend (1979):
1. Physical
restructuring,
2. Over
harvesting,
3. Waste
residuals,
4. Introduction
of exotic species, and
5. Global
change.
1.
Physical Restructuring :
Activities such as wetland drainage, removal of shoals in lakes, damming of
rivers, and road construction fragment the landscape and alter and damage
critical habitat. These activities also disrupt nutrient cycling, and cause the
loss of biodiversity.
2.
Over harvesting :
Overexploitation is commonplace when it comes to harvesting of wildlife,
fisheries, and forests. Over long periods of time, stocks of preferred species
are reduced. For example, the giant redwoods that once thrived along the California
3.
Waste Residuals :
Discharges from municipal, industrial, and agricultural sources into the air,
water, and land have severely compromised many of the earth's ecosystems. The
effects are particularly apparent in aquatic ecosystems. In some lakes that
lack a natural buffering capacity, acid precipitation has eliminated most of
the fish and other organisms. While the visual effect appears beneficial (water
clarity goes up) the impact on ecosystem health is devastating. Systems that
once contained a variety of organisms and were highly productive (biologically)
become devoid of most lifeforms except for a few acid-tolerant bacteria and
sediment-dwelling organisms.
4.
Introduction of Exotic Species :
The spread of exotics has become a problem in almost every ecosystem of the
world. Transporting species from their native habitat to entirely new
ecosystems can wreck havoc, as the new environments are often without natural
checks and balances for the new species. In the Great Lakes Basin Great
Lakes further destabilized the native fish community. The sea
lamprey contributed to the demise of the deepwater benthic fish community by
preying on lake trout, whitefish, and burbot. This contributed to a shift in
the fish community from one that had been dominated by large benthic to one
dominated by small pelagic (fish found in the upper layers of the lake
profile). This shift from bottom-dwelling fish (benthic) to surface-dwelling
fish (pelagic) has now been partially reversed by yet another accidental
introduction of an exotic: the zebra mussel. As the zebra mussel is a highly
efficient filter of both phytoplankton and zooplankton, its presence has
reduced the available food in the surface waters for pelagic fish.
However, while the benthic fish
community has gained back its dominance, the preferred benthic fish species
have not yet recovered owing to the degree of initial degradation. Overall, the
increasing dominance by exotics not only altered the ecology, but also reduced
significantly the commercial value of the fisheries.
5.
Global Change :
Rapid climate change (or climate warming) is an emerging potential global
stress on all of the earth's ecosystems. In evolutionary time, there have of
course been large fluctuations in climate. However, for the most part these
fluctuations have occurred gradually over long periods of time. Rapid climate
change is an entirely different matter. By altering both averages and extremes
in precipitation, temperature, and storm events, and by destabilizing the El
Niño Southern Oscillation (ENSO), which controls weather patterns over much of
the southern Pacific region, many ecosystem processes can become significantly
altered. Excessive periods of drought or unusually heavy rains and flooding
will exceed the tolerance for many species, thus changing the biotic
composition. Flooding and unusually high winds contribute to soil erosion, and
at the same time add to nutrient load in rivers and coastal waters.
These anthropogenic stresses have
compromised ecosystem function in most regions of the world, resulting in
ecosystem distress syndrome (EDS). EDS is characterized by a group of signs,
including abnormalities in nutrient cycling, productivity, species diversity
and richness, biotic structure, disease prevalence, soil fertility, and so on.
The consequences of these changes for human health are not inconsiderable.
Impoverished biotic communities are natural harbors for pathogens that affect
humans and other species.
ECOSYSTEM HEALTH AND HUMAN HEALTH
An
important aspect of ecosystem degradation is the associated increased risk to
human health. Traditionally, the concern has been with contaminants,
particularly industrial chemicals that can have adverse impacts on human
development, neurological functions, reproductive functions, and that appear to
be causative agents in a variety of carcinomas. In addition to these serious
environmental concerns (where the remedies are often technological, including
engineering solutions to reduce the release of contaminants), there are a large
number of other risks to human health stemming from ecological imbalance.
Ecosystem
distress syndrome results in the loss of valued ecosystem services, including
flood control, water quality, air quality, fish and wildlife diversity, and
recreation. One of the major signs of EDS is increased disease incidence, both
in humans and other species. Human population health should thus be viewed
within an ecological context as an expression of the integrity and health of
the life-supporting capacity of the environment.
Ecological
imbalances triggered by global climate change and other causes are responsible
for increased human health risks.
Climate
Change and Vector-Borne Diseases. The global infectious disease burden
is on the order of several hundred million cases per year. Many vector-borne
diseases are climate sensitive. Malaria, dengue fever, hantavirus pulmonary
syndrome, and various forms of viral encephalitis are all in this category. All
these diseases are the result of arthropod-borne viruses (arboviruses) which
are transmitted to humans as a result of bites from blood-sucking arthropods.
Global
climate change—particularly as it impacts both temperatures and precipitation—is
highly correlated with the prevalence of vector-borne diseases. For example,
viruses carried by mosquitoes, ticks, and other blood-sucking arthropods
generally have increased transmission rates with rising temperatures. St. Louis
encephalitis (SLE) serves as an example. The mosquito Culex tarsalis
carries this virus. The percentage of bites that results in transmission of SLE
is dependent on temperature, with greater transmission at higher temperatures.
The
temperature dependence of vector-borne diseases is also well illustrated with
malaria. Malaria is endemic throughout the tropics, with a high prevalence in
Africa, the Indian subcontinent, Southeast Asia, and parts of South and Central
America and Mexico
The
climate sensitivity of malaria arises owing to the nature of the interactions
of parasites, vectors, and hosts, all of which impact the ultimate transmission
rates to humans. The gestation time required for the parasite to become fully
developed within the mosquito host (a process termed sporogony) is from eight
to thirty-five days. When temperatures are in the range of 20°C to 27°C, the
gestation time is reduced. Rainfall and humidity also have an influence. Both
drought and heavy rains tend to reduce the population of mosquitoes that serve
as vectors for malaria. In drier regions of the tropics, low rainfall and
humidity restricts the survival of mosquitoes. Severe flooding can result in
scouring of rivers and destruction of the breeding habitats for the mosquito
vector, while intermediate rainfall enhances vector production.
Ecological
Imbalances. Cholera is a serious and potentially fatal disease that is
caused by the bacterium Vibrio cholerae. While not nearly so prevalent
as malaria, cases are nonetheless numerous. In 1993, there were 296,206 new
cases of cholera reported in South America; 9,280 cases were reported in Mexico ; 62,964 cases in Africa; and 64,599 cases
in Asia . Most outbreaks in Asia, Africa, and South America have originated in coastal areas. Symptoms
of cholera include explosive watery diarrhea, vomiting, and abdominal pain. The
most recent pandemic of cholera involved more regions than at any previous time
in the twentieth century. The disease remains endemic in India , Bangladesh ,
and Africa . Vibrio cholerae has also
been found in the United States —in
the Gulf Coast
region of Texas , Louisiana ,
and Florida ; the Chesapeake Bay area; and the California
The
increase in prevalence of V. cholerae has been strongly linked to
degraded coastal marine environments. Nutrient-enriched warmer coastal waters,
resulting from a combination of climate change and the use of fertilizers,
provides an ideal environment for reproduction and dissemination of V.
cholerae. Recent outbreaks of cholera in Bangladesh Bangladesh
Antibiotic
Resistance and Agricultural Practice Antibiotic resistance is a growing
threat to public health. Antibiotic resistant strains of Streptococcus
pneumoniae, a common bacterial pathogen in humans and a leading cause of
many infections, including chronic bronchitis, pneumonia, and meningitis, have
greatly increased in prevalence since the mid-1970s. In some regions of the
world, up to 70 percent of bacterial isolates taken from patients proved
resistant to penicillin and other b-lactam antibiotics. The use of large
quantities of antibiotics in agriculture and aquaculture appears to have been a
key factor in the development of antibiotic resistance by pathogens in farm
animals that subsequently may also infect humans. One of the most serious risks
to human health from such practices is vancomycin-resistant enterococci. The
use of avoparcin, an animal growth promoter, appears to have compromised the
utility of vancomycin, the last antibiotic effective against
multi-drug-resistant bacteria. In areas where avoparcin has been used, such as
on farms in Denmark and Germany United Kingdom
Food
and Water Security. Agricultural practices are also
responsible for a growing number of threats to public health. Some of these are
related to inadequate waste management, which has resulted in parasites and
bacteria entering water supplies. Others are of entirely different origins and
involve apparent transfer across species of pathogens that affect both animals
and humans. The most recent and spectacular example is mad cow disease, known
as variant Creutzfeldt-Jakob disease in humans, a neuro-degenerative condition
that, in humans, is ultimately fatal. The first case of Bovine Spongiform
Encephalopathy (BSE), the animal form of the disease, was identified in Southern England in November 1981. By the fall of 2000,
an outbreak had also occurred in France ,
and isolated cases appeared in Germany ,
Switzerland , and Spain Europe were
attributed to what has come to be commonly called mad cow disease.
Improper
manure management was the likely source of the outbreak of E. coli
0157:H7 in Walkerton , Ontario , Canada
ECOSYSTEM RESTORATION
Ecosystem
pathology in some cases can be reversed simply by removing the source of
stress. In cases, for example, where ecosystem degradation is the result of
point-source additions of nutrients or toxic chemicals, removal of these
stresses may result in considerable recovery of ecosystem health. A classic
case is Lake Washington (near Seattle ,
Washington
In
cases where it is not feasible to remove the source of stress, more innovative
engineering solutions have been tried. For example, in the Kyrönjoki and Lestijoki Rivers
in western Finland
More
radical treatments for damaged ecosystems involve "ecosystem
surgery." In some cases, invading exotic vegetation (such as mangroves in Hawaii North America where wetlands have been severely depleted
owing to farming, urbanization, and industrial activity, efforts have been made
to establish new wetlands.
More
often than not, however, reversing ecosystem pathology is not possible. Efforts
to restore the indigenous grasslands in the Jornada
Experimental Range
in the southwestern United
States
Even
where it has been possible to restore some of the ecological functions of
degraded ecosystems, and thus improve ecosystem health, the restoration seldom
results in reestablishment of the pristine biotic community. The best that can
be achieved in most cases is reestablishment of the key ecological functions
that provide the required ecosystem services, such as the regulation of water,
primary and secondary productivity, nutrient cycling, and pollination. In all
such efforts, key indicators of ecosystem health (vigor, productivity, and
resilience) are essential to monitor progress. Standard ecological indicators
can be used for this purpose (e.g., measures of productivity, species
composition, nutrient flows, soil fertility) along with socioeconomic and human
health indicators.
Experience
in efforts to restore highly damaged ecosystems suggests that ecosystem-health
prevention is far more effective than restoration. For marine ecosystems,
setting aside protective zones that afford a sanctuary for fish and wildlife
has considerable promise. Many countries are adopting policies to establish
such areas with the prospect that these healthy regions can serve as a
reservoir for biota that have become depleted in the unprotected areas. Yet
this remedy is not without its limits. Restoring ecosystem health is not simply
a matter of replenishing lost or damaged biota. It is also a matter of
reestablishing the complex interactions among ecosystem lifeforms. Having a
ready source of healthy biota that could potentially recolonize damaged
ecosystems is important, but it is only part of the solution.
PROBLEMS WITH RESTORATION
Many people take the view that ecosystem restoration is
impractical. One reason for this view is that restoration of ecosystems does
not always work. There are many reasons for restoration failure. Hilderbrand et
al. (2005) point out that many times uncertainty (about ecosystem functions,
species relationships, and such) is not addressed, and that the time-scales set
out for ‘complete’ restoration are unreasonably short. Other times an ecosystem
may be so degraded that abandonment (allowing an injured ecosystem to recover
on its own) may be the wisest option. Other negative impacts of ecosystem
restoration can include the introduction of large predators, which may inspire
doubts in people’s safety, and plants, some requiring disturbance regimes such
as regular fires. High economic costs can also be a perceived as a negative
impact of the restoration process. Public opinion is very important in the
feasibility of a restoration; if the public believes that the costs of
restoration outweigh the benefits, then support for that project is unlikely to
be big, especially in small towns. In these cases people might be ready to
follow the abandonment route and let the ecosystem recover on its own, which
can sometimes occur relatively quickly.
Many failures have occurred in past restoration projects,
many times because clear goals were not set out as the aim of the restoration.
This may be because, as Peter Alpert says, “people may not [always] know how
to manage natural systems effectively”. Also many assumptions are made
about myths of restoration such as the carbon copy, where a restoration plan,
which worked in one area, is applied to another with the same results expected,
but not realized.
PREVENTION OF ECOSYSTEM DISRUPTIONS
Given
the difficulties in reversing ecosystem degradation, and the many associated
risks that arise with the loss of ecosystem health, the most effective approach
is simply the prevention of ecosystem disruption. However, like many
common-sense approaches, this is easier said than done. In both developed and
developing countries there is a strong inclination to continue economic growth,
even at the cost of severe environmental damage. Apart from selfish
motivations, the argument is made that economic growth has many obvious health
benefits, such as providing more efficient means of distributing food supplies,
providing more plentiful food, and providing better health services and funding
for research to improve standards of living. These are indeed benefits of
economic development, and have led to substantial increases in health status
worldwide.
However,
at the dawn of the twenty-first century, the past is not necessarily the best
guide to the future. The human population is at an alltime high, and associated
pressures of human activity have led to increasing degradation of the earth's
ecosystems. As ultimately healthy ecosystems are essential for life of all
biota, including humans, current global and regional trends are ominous. Under
these circumstances, a tradeoff between immediate material gains and long-term
sustainability of humans on the planet may be the only option. If so, the
solution to sustaining human health and ecosystem health becomes one of
devising a new politic that places sustaining life-support systems as a
precondition for betterment of the human condition.
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