Rachel Carson loved all forms of wildlife and treasured the environment on which we all depend.
- Ecosystem Services
- Wildlife, Pesticides and People Conference
- Frogs and Pesticides
Source of Wonder, Source of Strength - Our Wildlife Workforce
"All these small creatures are working - working in sun and rain, during the hours of darkness, even when winter's grip has dampened down the fires of life to mere embers. Then this vital force is merely smoldering, awaiting the time to flare again into activity when spring awakens the insect world." ~ Silent Spring, p. 251
Although Rachel Carson was referring to insects in this case, wildlife as a whole represents a vital force. In order for this force to continue successfully it needs our help through creation of a planetary partnership to conserve and protect the work of wildlife.
Not only does nature sustain us physically, it can also engender in us, if we allow it, a "... sense of wonder so indestructible that it would last throughout life, as an unfailing antidote against .. alienation from the sources of our strength." ~ The Sense of Wonder
This source of wonder and strength so precious to Rachel Carson is today threatened by the very practices against which she struggled. Pesticide use continues to contaminate our planet, reducing nature's essential services.
The functioning ecosystems that we rely on for clean water, clean air and healthy food consist of plants producing oxygen and removing carbon dioxide, insects and others pollinating plants, insects (like dragonflies) controlling pests (like mosquitoes), as well as insects and fungi recycling organic matter. In addition there are the microbes, which as Rachel Carson wrote "...include not only disease organisms but those that destroy waste, make soils fertile, and enter into countless biological processes... " ~ Silent Spring, p.289
Pesticide Problems Continue
With its egg shell thinning, and resulting declines of Bald Eagle, Peregrine Falcon, Pelican, Osprey, and Cormorant populations, DDT remains a familiar story. Since Rachel Carson's eloquent plea for protection of wildlife in Silent Spring was followed by the ban on DDT and other organochlorines, many people came to believe that pesticides were effectively eliminated as hazards for our own wildlife.
Today, unheeded by many Americans, migratory birds are threatened directly by insecticides acting as nerve poisons and by rodenticides with various toxic modes in the US and abroad. Indirect harm can result from various pesticides reducing birds' food and habitat.
Some of these indirect threats can take decades to uncover. Such was the case with the link between the herbicides applied to fields and the elimination of the partridge populations from the grain-growing farms in Sussex, England. The association was established through studying data collected over a 30 year time span.
Experts are starting to try quantifying not only the immediate mortality from pesticides but also the long term changes that can lead to reduced reproduction and population decreases. At a recent meeting in Laurel, Maryland a single organophosphate insecticide, carbofuran, was estimated to kill 34 million migratory birds yearly when both direct and indirect toxic actions are considered (Dr.R. O'Connor, "Pesticide Effects on Birds: Beyond the Tip of the Iceberg). Based on direct toxicity alone scientists estimate that carbofuran can kill between 8 and 9 million birds yearly.
Incident reports and application information have resulted in estimates of wildlife fatalities from pesticides and include 72 million bird deaths at a cost to society of over $2.1 billion annually (personal communication, 2001) and 14 million fish deaths at a cost of $56 million. The estimated cost to society from pesticides' damage to insects, both those that are pollinators as well as those that are the natural enemies of pests, is given as $700 million annually. ~ Dr. David Pimentel, Keynote Address, Wildlife Pesticides and People Conference
Wildlife Working Under the Pesticide Threat
Without requiring payment for services wildlife workers can create healthy ecosystems. Here are some examples of their contributions and the chemical pesticides that reduce their effectiveness.
These organisms live in the roots of plants where they help with nutrient assimilation and contribute to soil fertility. They can be poisoned by fungicides and herbicides.
Wild cherry trees
Listed among the top 5 woody plants of importance to wildlife, these trees serve as sources of nectar and food for wildlife. Their branches provide windbreaks and shade. Their roots help stabilize the soil and prevent erosion.
A new type of low-dose herbicide from the sulfonylurea class has been found to reduce the trees' ability to reproduce and produce seeds with scarcely any other evidence of injury. This has been found to occur with levels of a sulfonylurea at 1/500th the recommended dose. Commercial growers have reported crop losses after the introduction of sulfonylurea-type herbicides.
Wild honey bees
These are among the organisms providing pollination, an essential service to seed-bearing plants. One third of all human food is dependent on pollinators. Most insecticides are harmful to bees and indicate so on their labels. Herbicides can damage bee communities by destroying nectar sources.
Tiny zooplankton such as the water flea comprise this highly valuable group. These animals feed on phytoplankton and insects (including mosquito larvae). They also serve as food sources for other animals. Five copepod species make up 95% of the biomass of the Chesapeake Bay. Certain copepods can be killed by organophosphate insecticides such as chlorpyrifos and diazinon at levels of parts per trillion. Copepods are among the most vulnerable organisms to pesticide poisoning.
These are predators that do not sting humans but can effectively control caterpillars, borers and tomato hornworrns by laying eggs in the body cavities of these pest insects. Many chemical insecticides harm the parasitic wasps and other beneficial insects. Herbicides can also destroy the food sources and habitat for the intermediate life stages of these natural enemies.
Neotropical migratory songbirds
"Unsung heroes of northern forests protecting them from foliage-eating menaces" is how Dr. Russ Greenberg describes this group of beautiful and useful birds. In addition they delight us with their songs. Baltimore orioles, among the sweetest of singers, are also capable of destroying whole colonies of tent caterpillars that are said to comprise 35% of the birds' diets.
In the field through directly encountering pesticide spraying or eating poisoned food, songbirds can be killed outright. Non-fatal exposures can alter critical responses including predator avoidance, feeding habits, reproduction and other behavior essential for survival.
Orioles have been deprived of essential winter habitat in Central America where coffee grown without the shade of tall trees requires synthetic pesticide and fertilizer input. Rachel Carson Council's brochure, "A Bird Lover's Guide to Good Coffee," calls for the purchase of shade-grown organic coffee by all those who cherish these wonderful creatures.
Salmon and other fish
As adults, fish serve as food for humans and other animals. Freshwater fish eat mosquito larvae. In their early life stages they are food for other aquatic animals. Of the 18 major lawn care chemicals, 85% are toxic to fish (according to the Basic Guide to Pesticides). From the most recent EPA data on pesticide use, of the top 10 chemical pesticides used in agriculture, 90% are toxic to fish (Basic Guide to Pesticides).
Salmon can be harmed by the commonly-used insecticide diazinon at concentrations in the water too low to be lethal. At such levels diazinon can actually damage the salmons' ability to avoid predation and to return to the streams of their birth through their legendary homing ability. These water concentrations of diazinon do not produce easily detected changes in the fish. Fish are considered as the third most vulnerable group of animals in terms of chemical pesticide toxicity after insects and crustaceans.
They are a food source for humans and for other members of the ecosystem. It has been estimated that before 1880 resident oysters in the Chesapeake Bay were able to filter all the Bay's water in 2-3 days. In 1988 the time required for oysters to provide the same service was estimated at 325 days, or 100 fold longer (RCC News #91). It may be even longer in 2001.
In a recent report in the journal Science, oysters were designated as being the controlling species in the Chesapeake Bay, the organisms on which the health of the Bay is most dependent (Jackson, J. et al, "Historical overfishing and the recent collapse of coastal ecosystems," Science (293), 7/27/2001, pp.629-638).
One of the most widely used herbicides, atrazine, may inhibit the growth of a type of phytoplankton serving as a food for oysters. The herbicides simazine and 2,4-D are moderately toxic for oysters (Basic Guide to Pesticides). All of those pesticides mentioned above have been found in the Chesapeake Bay or its tributaries.
We need to make sure there are healthy workplaces free of the chemicals that can stop this "vital force" from working.Ultimately, we are far better served with wildlife doing the jobs they have performed for centuries than with technological substitutes that can be less successful and are ultimately more costly.
Toxicity studies by which pesticides are evaluated before registration can fail to detect the actual conditions under which wildlife encounter these contaminants or their ecosystem impacts. The regulations under which pesticides are registered may allow environmental effects that are detected to be disregarded.
The Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), the law under which pesticides are registered, is an administrative act designed to regulate the use of toxic pesticides for the purpose of promoting the economic interests of agriculture.
FIFRA allows registration of chemicals if they "will not generally cause unreasonable adverse effects on the environment." The decision on whether or not to register a pesticide is made not by scientists but by managers who can ultimately disregard the hazards to wildlife if they deem the chemical's benefit to agriculture overrides its risk.
Taking our cue from Rachel Carson, citizens remaining mindful of the sources of wonder and strength in the natural world need to create a planetary partnership protecting the earth's wild workers so that our own society with its human workforce can be sustained. ~ Diana Post VMD
Pesticides Harming Frogs?
In an article in The New York Times (6/23/2005), garden columnist Anne Raver described a farm field that had been taken out of production and planted with native grasses as part of a federal program "to keep pesticides and nitrates out of the watershed and to control erosion." She mentioned that when the field previously had been in production, frogs and peepers "had all disappeared ... possibly from pesticide use."
Current research supports this assertion. A number of the most commonly-used pesticides have been found to harm frogs. They include atrazine, diazinon, malathion and most recently, the herbicide RoundUp. In 2005, Pennsylvania researcher Dr. Relyea reported that RoundUp, when it was applied at recommended levels, was lethal to some frog species (Ecological Applications 2005 (v15:4)).
There is an increasing level of pesticide usage around the globe. The finding that RoundUp can harm some amphibians greatly enhances the likelihood that harm from exposure to pesticides is a factor in the widespread decrease in numbers and species of amphibians. In areas where ecosystems are being preserved or restored, methods to eliminate unwanted organisms need to be chosen that do not pose a hazard to frogs.