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The general public is becoming much more knowledgeable about the
importance of conservation and biodiversity. Many groups of
organisms are conspicuous and recognizable to the public such as game
animals, sport fishes and most birds and there have been initiatives
that seek to preserve and manage the biodiversity of these groups. For
other less conspicuous groups, such as freshwater mussels, there is a
growing awareness of the magnitude of population reductions and even
potential extinction of a large percentage of the species in North
America. For insects, however, public policy has largely focused on
methods to reduce or eliminate pestiferous species. Little
attention has been paid the effects of the control methods and
modifications to the environment on non-target insect species that make
up the greatest proportion of insect fauna. Most non-target
species are ecologically important in that they may enhance
productivity of natural systems and maintain ecological balance,
thereby providing essential "goods and services" for a natural and
healthy environment. In addition, insects contain a treasure
house of unevaluated and unknown natural compounds with great potential
to benefit humankind in the form of new materials (e.g., spider silk)
and pharmaceuticals (e.g., honey bee propolis). The current rate
of species extinctions is rapidly depleting this irreplaceable natural
resource. The time has come to allocate resources to conserve the
existing biodiversity of insects and their relatives, and to expand
efforts to discover and evaluate their natural chemicals for use in
medicine, agriculture and industry.
Conservation of insect species is made more difficult by dramatic
environmental changes associated with human activity. Large and
small-scale fragmentation of habitats is now common as urbanization
continues unabated. Increasing concentrations of atmospheric CO2 will
substantially alter the interactions between insects and
plants. These changes in insect-plant relationships,
particularly those associated with suitability and nutritional status
of plants, are expected to have significant effects on biological
control of insects by other parasitic and predatory insects, likely
leading to large scale outbreaks of insect pest populations. From
the point of view of insect diversity, distribution, and conservation,
the biological effects of urbanization and elevated CO2 levels will
greatly complicate management activities. In addition, such major
changes will impact critical aspects of ecosystem function, thereby
influencing the quality of life for plants, animals and human
populations.
Insects are critical components of most terrestrial and fresh water
ecosystems. They serve not only as an important part of the food
web for higher trophic levels, but as key herbivores and
recyclers. Despite these diverse roles, little is known about how
pollutants affect insects. In addition, there is a critical
shortage of information on effects of multiple toxins: over 95% of all
toxicological studies only examine the impact of individual
chemicals.
Problems with pollution are not new; air and soil contamination have
been reported for thousands of years. However, the problem has
become substantially worse since the Industrial Revolution, with the
large-scale production and transport of many toxic materials.
Even in situations where pollution has been largely eliminated, a
'legacy' of contamination may still exist. Thus, the
environmental effects of pollution are likely to continue for the
foreseeable future.
Solving our existing problems of environmental contamination and
mitigating the effects of contaminants on living organisms are
difficult because of the incredible variety of sources and forms of
pollution. Even an abbreviated list of pollutants would
include thousands of industrial by-products, pesticide residues from
chemicals that have been banned from use, a variety of toxic metals and
chemicals in mining waste, many compounds produced by burning fossil
fuels, the by-products of warfare, chemicals used in electrical
generation/transport machinery, fuel additives, as well as a host of
other materials. Each pollutant has the potential to disrupt
ecosystems. Some have minimal effects; others have contaminated
soils so that plants or animals from these areas cannot be eaten.
A few have created wastelands, where the ground has become too toxic to
support even the most basic organisms in an ecosystem.
Terrestrial arthropods are critical to the functioning of
ecosystems. Because they are at the base of the food web, changes
in population densities of arthropods can have profound effects on
higher-level organisms that depend on them. Insects and their
relatives are used as food by many birds and mammals. Many
arthropods are beneficial, serving to keep pest populations under
control, thereby preventing damaging outbreaks. Others pollinate
plants, disseminate seeds, and produce structures used by countless
other organisms. Disruption of any of these activities can have
disastrous effects on an ecosystem. Thus, arthropods are often
the first animals examined when ecosystems become polluted.
Insects are similarly important in freshwater aquatic ecosystems.
Water quality and wetland reclamation are critical 21st century issues
in the United States. Macro invertebrates, most notably aquatic
insects, have been found to be reliable and efficient indicators of
water quality. Evaluating changes in macro invertebrate
composition in creeks, streams, lakes and wetlands provides critical
scientific data to inform decision-making related to pollution
abatement programs and habitat modification. Data can also be
used to provide an early warning of both intentional and unintentional
releases of environmental contaminants and toxicants. Pilot
programs around the country are utilizing citizen-monitoring programs
to augment credible scientific data that evaluate the biological health
of the nation’s fresh water resource.
Entomological expertise is essential to these environmental monitoring
efforts. Little is known about the invertebrate composition of
many of our natural water systems and their relationship to water
quality indicators such as organic matter content and nutrient
enrichment, or the key roles they play in maintaining healthy
environments. Therefore, it is necessary to support initiatives to
discover undescribed species, learn about their life cycles,
populations, seasonality, food requirements and natural predators so
that they can better serve as environmental monitors and early warning
indicators. In addition, entomologists should be enlisted to help
train and coordinate volunteer citizen-monitoring groups to enable them
to provide scientifically rigorous information.
Addressing environmental challenges would be relatively easy if
resources and time were unlimited, but this is never the case. As
a result, policy makers and resource managers are often asked to decide
how to allocate (severely) limited resources to achieve the greatest
good. Ecological risk analysis provides a framework to address
this challenge. Ecological risk analysis consists of risk
assessment, risk communication, and risk management. In general
terms, these components provide decision makers with an understanding
of the likelihood that an agent may cause an unwanted ecological effect
in either a natural or managed ecosystem, a critical evaluation of
different options to control or mitigate the stressor, and a vehicle to
communicate this information and the ultimate management decision to
the public. Risk assessment can be used to examine the consequences of
transgenic crops for non-target species, determine the likelihood that
an insect can be used for bioterrorism, assess the impact of
importation of plants and products and their associated insect fauna,
evaluate climatic change by looking at changes in insect species
distribution, evaluate ecosystem health using insects as bioindicators,
and assess pesticide safety using insect indicators.
Due to the complexity of urban environments and the diversity of urban
pests, numerous pesticide compounds have been made available for use by
homeowners and pest management companies. These compounds are
applied at higher rates in urban environments than agricultural
environments. Human exposure to these compounds in their living
areas, drinking water, and food is an important concern. Although
indoor use of pesticides appears to have decreased in recent years,
surveys show that most homes use at least one pesticide indoors per
year. Exposure to multiple pesticides at any given time is also
possible due to inadvertent introduction of pesticide residues from
outside sources such as soil, air, etc. Pesticide application to
gardens, landscaping, and yards not only increases the risk of
pesticide exposure when we spend time in these living areas, but also
increases the risk of inadvertent introduction of pesticide compounds
into indoor areas. Most recently, concern about mosquito-borne
disease (e.g. West Nile virus) is leading to increased use of
insecticides for controlling adult mosquito populations.
Pesticides are found frequently in surface water and often with higher
frequency and at higher concentrations in urban streams than
agricultural streams. Insecticide concentrations in many urban
streams exceed water quality guidelines for the protection of fish and
other aquatic organisms. Although state and federal monitoring
confirm the presence of various pesticides in urban groundwater, the
amounts of these compounds usually do not exceed government water
quality guidelines for drinking water.
As the use of persistent compounds has decreased in response to human
health concerns, there has been an accompanying increase in the use of
less persistent compounds, resulting in a qualitative rather than
quantitative change in pesticide use patterns. Integrated pest
management (IPM) strategies, which seek a quantitative change in
pesticide use through pest prevention, sanitation, natural enemy
conservation, and reduced pesticide application, are being adopted in
urban environments. A goal of effective IPM strategies for the
urban environment is to minimized human exposure to pesticide compounds
in their living areas, drinking water, and food.
Nutrient enrichment of surface waters is a widespread and pervasive
form of water pollution that is particularly severe in large urban
areas with high human populations and concentrated industry.
Despite substantial research and development efforts by the U.S.
Environmental Protection Agency to mitigate the enrichment of streams,
rivers, lakes and reservoirs, nutrient enrichment still impairs high
percentages of stream and river miles in most states, and nearly all
river miles in others.
Substantial and unwanted increases in densities of insects that breed
in these aquatic systems is one important impact of nutrient
enrichment. Insect population increases are the combined result
of increased particulate organic matter from wastewater treatment
plants, which serve as food for the insects, and high microbial growth
that reduces dissolved oxygen resulting in lower fish densities or
their complete absence. A lowered fish density reduces predation of
insects, facilitating even higher populations of aquatic insects.
Insect species that survive and proliferate are typically biting and
non-biting flies, which can develop population densities exceeding
30,000 individuals/square meter and emergences in excess of 400
adults/square meter per day during summer. Several of the more common
species in severely nutrient-enriched habitats contain hemoglobins
and/or other complex organic molecules that are potent environmental
allergens, causing mild to severe reactions in sensitized individuals.
In addition, many of the fly species are attracted to lights and become
nuisances at door lights, business entrances and deck lights after
dark.
We currently have a poor ability to accurately predict changes in
levels of troublesome fly species as treatment of sewage waste improves
and facilities are upgraded or decommissioned. Developing this
information, will allow waste treatment programs to develop best
practices that fine-tune their pollution reduction efforts.
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