Publications: 2000–2009

Abstract: Cyclopoid copepods and mosquito larvae were surveyed in southwestern Louisiana rice fields. Almost every rice field had a natural population of Mesocyclops ruttneri, Acanthocyclops vernalis, or Macrocyclops albidus. Judging from the abundance of pupae, 29% of the fields were responsible for virtually all Anopheles quadrimaculatus production, apparently because larval mortality suppressed production in the other fields. Mesocyclops ruttneri had the strongest negative association of naturally occurring copepod populations with An. quadrimaculatus larvae, though a few fields with M. ruttneri had substantial Anopheles production. Macrocyclops albidus, M. ruttneri, Mesocyclops edax, and Mesocyclops longisetus were introduced to experimental rice field plots. It took two months for the introduced copepods to build up their numbers; Anopheles larvae then disappeared from all treated plots while larvae continued to be present in the adjacent control field. Copepods were observed to kill the following number of first instar An. quadrimaculatus larvae in the laboratory: Mesocyclops ruttneri (36 larvae/day), Macrocyclops albidus (23 larvae/day), Mesocyclops longisetus (24 larvae/day), and Acanthocyclops vernalis (15 larvae/day). It is concluded that introducing select species of copepods and encouraging their populations offer possibilities for contributing to Anopheles control in rice fields.

Abstract: Natural populations of three larvivorous copepod species live in residential roadside ditches in Louisiana: Macrocyclops albidus, Acanthocyclops vernalis, and Megacyclops latipes. Macrocyclops is most common and killed an average of 27 first-instar Culex quinquefasciatus larvae/copepod/day in the laboratory. Although severe pollution from septic tank effluent in some parts of the ditches creates havens for Cx. quinquefasciatus production by excluding predatory copepods and fish (Gambusia affinis), Macrocyclops and the fish substantially reduce Cx. quinquefasciatus larval survival when present where pollution is not so severe. At natural abundance, Macrocyclops reduced the survival of Cx. quinquefasciatus larvae (during their first four days) to 2.6%, compared with 46% survival in controls without Macrocyclops. During one year of field observation, Macrocyclops was common in the spring but disappeared during the summer when fish (which prey on copepods) appeared in many ditches, reduced water flows led to more severe pollution, and water temperatures in very shallow water were sometimes higher than Macrocyclops could survive. Macrocyclops reappeared in many ditches during autumn and winter, when water temperatures and pollution declined and fish disappeared. Introduction of Macrocyclops to ditches in October accelerated its reappearance during autumn and winter and reduced the number of sites with Cx. quinquefasciatus larvae to one-quarter the number in control ditches. The most effective way to control Cx. quinquefasciatus is to eliminate pollution so predators like fish and copepods can live throughout the ditches, but timely introduction of fish and copepods could also contribute to control. More experience will be necessary to ascertain whether copepod introductions are cost effective.

Overview: The story of Dengue Hemorrhagic Fever, an “emergent” disease known only since 1950, illustrates the benefits that are possible with local community action and ecological management. Dengue Hemorrhagic Fever is transmitted by mosquitoes that breed in water storage tanks and other water-filled containers around people’s homes. There is no vaccine or medicine for this virus; the only way to prevent the disease is to get rid of the mosquitoes. Initially spectacular success controlling the mosquitoes with DDT during the 1950s and 1960s was not sustainable because the mosquitoes evolved resistance to DDT. Other pesticides have gone into use, but there has been no overall reduction in the disease. Nearly one hundred million people in tropical Asia and Latin America are now afflicted with dengue each year, about one-half million children are hospitalized annually with life-threatening Dengue Hemorrhagic Fever, and thousands die. The pesticide-based strategy of the last fifty years has been a failure, but what else can be done? Ecological management promises to be more effective and sustainable. The copepod Mesocyclops provides an example. This tiny crustacean kills virtually all the mosquito larvae wherever it is in water-filled containers where the mosquitoes breed. Vietnam has mounted a campaign to distribute copepods to thousands of villages with a dengue problem. The mosquito and the disease have disappeared from every village that uses this predator. The key to success is strong community organization to ensure that everyone in a village uses the copepods.

Overview: An environmental tipping point is a part of the human-environment system that can lever far-reaching change in the system. A change at the tipping point sets in motion mutually reinforcing feedback loops that propel the system on a completely new course. An environmental tipping point perspective can help to cope with the complexity of environmental problems by providing a lens for:

• comprehending why some environmental problems are so difficult to solve;
• understanding environmental success stories in a way that points to concrete measures for strengthening ecological security and sustainability;
• creating a more functional and productive public dialogue for ecological security and sustainability.

Apo Island in the Philippines provides an example of environmental tipping points in action. The introduction of destructive fishing methods was a "negative tip" that set the regional fishery on a forty-year downward spiral to virtual collapse. Apo Island escaped the downward spiral with a "positive tip" - the creation of a small marine sanctuary - which set in motion a cascade of ecological and social changes that restored declining fish stocks and returned the island's marine ecosystem to health. Japan had a similar experience with severe deforestation during the Seventeenth Century. Extension of traditional village cooperation to forest management stimulated the development and dissemination of new silvicultural techniques and the creation of new social institutions that set Japan on a course of sustainable forest use.

Overview: This article examines environmental tipping points through three case studies: restoration of the coral-reef fishery at Apo Island in the Philippines, revival of traditional rainwater harvesting in Rajasthan, India, and the development of community gardens in New York City. It traces the environmental and social conditions that preceded each initiative, the actions that helped redirect those conditions, and the ecological and community changes that followed. Comparing the three cases, the authors identify recurring patterns in which relatively focused actions generate reinforcing cycles of recovery within interconnected social and ecological systems. The article concludes with a set of questions for identifying potential tipping points and examining where interventions might redirect reinforcing cycles of decline.

Overview: This article examines the experience of Punukula, a cotton-growing village in Andhra Pradesh, India, as it moved away from dependence on chemical pesticides. It traces how increasing pesticide use became associated with pest resistance, rising production costs, debt, health problems, and other pressures on village households. The article then describes the introduction of non-pesticidal management (NPM), including the use of neem and a range of biological, agricultural, and monitoring practices for controlling crop pests. It follows the expansion of these practices throughout the village and describes the environmental, economic, health, and community changes that accompanied the transition, culminating in Punukula’s declaration as a pesticide-free village and its subsequent role in promoting NPM to other communities.

Abstract: Cyclopoid copepods have proved more effective for practical mosquito control than any other invertebrate predator of mosquito larvae. Their operational potential is enhanced by the fact that mass production is relatively easy and inexpensive. The exceptional potential of copepods for mosquito control was first realized about 25 years ago. Since then, laboratory experiments with copepods and mosquito larvae around the world have shown: Only the larger copepod species (body length > 1.4 mm) are of practical use for mosquito control. They kill mainly 1st instar mosquitoes. The most effective species have the capacity to kill more than 40 Aedes larvae/copepod/day. They generally kill fewer Anopheles larvae and even fewer Culex larvae. Most field testing of copepods has been in Aedes container-breeding habitats. Field tests have shown that: The most effective copepod species maintain large populations in a container habitat for as long as there is water. They typically reduce Aedes production by 99-100%. They can cause local eradication of container-breeding Aedes mosquitoes if present in a high percentage of breeding sites. Field surveys in Anopheles, floodwater Aedes, and Culex breeding habitats have shown that natural copepod populations can substantially reduce, or even eliminate, mosquito production. Field trials in temporary pools, marshes, and rice fields have demonstrated that introduction of the right copepod species to the right habitat at the right time can eliminate Anopheles or floodwater Aedes larvae. As a rule, copepods cannot eliminate Culex production by themselves, but they can reinforce and augment control by other methods. The only large-scale operational use of copepods to date has been in Vietnam, which has achieved local eradication of Ae. aegypti in hundreds of villages. Conditions in Vietnam are particularly favorable because: Many Ae. aegypti breeding sites are water storage containers that are conspicuous and easily treated. Motivation to maintain copepods in containers for Ae. aegypti control is strong because of the high incidence of dengue hemorrhagic fever. Copepod use is effectively managed by women's associations already experienced with neighborhood health services. Copepods have the potential for local eradication of Ae. aegypti and Ae. albopictus in many other countries besides Vietnam. Professional capacity for copepod management and social institutions for community participation to help with implementation and maintenance are the main factors limiting broader use of copepods for operational mosquito control at the present time.

Abstract: Although most algae are nutritious food for mosquito larvae, some species kill the larvae when ingested in large quantities. Cyanobacteria (blue-green algae) that kill larvae do so by virtue of toxicity. While blue-green algae toxins may offer possibilities for delivery as larvicides, the toxicity of live blue-green algae does not seem consistent enough for live algae to be useful for mosquito control.

Certain species of green algae in the order Chlorococcales kill larvae primarily because they are indigestible. Where these algae are abundant in nature, larvae consume them to the exclusion of other food and then starve. Under the right circumstances, it is possible to introduce indigestible algae into a breeding habitat so they become abundant enough to render it unsuitable for mosquito production. The algae can persist for years, even if the habitat dries periodically. The main limitation of indigestible algae lies in the fact that, under certain conditions, they may not replace all the nutritious algae in the habitat. More research on techniques to ensure complete replacement will be necessary before indigestible algae can go into operational use for mosquito control.

Abstract: Juvenile turtles have the capacity to eat more than 500 3rd and 4th instar mosquitos per day. Keeping one turtle in each water-storage tank during field trials for a dengue-control project in Honduras eliminated all mosquito production from the tanks. In Louisiana, keeping turtles in residential roadside ditches polluted by septic-tank effluent reduced Culex quinquefasciatus larvae and pupae by more than 99%. Turtles can serve as alternate hosts for Salmonella when kept in small pet containers, but the available evidence indicates that turtles create no Salmonella hazard in water-storage tanks or other mosquito-breeding habitats. Although turtles would probably not be practical for mosquito control in roadside ditches, they could be effective in storm-water catch basins or holding ponds.

Overview: This article introduces the concept of Eco Tipping Points through two case studies of communities responding to environmental decline. It examines community-led restoration of mangrove forests and coastal fisheries in Trang Province, Thailand, and the development of a constructed wetland for wastewater treatment in Arcata, California. The article traces the environmental and social problems that preceded these efforts, the actions taken by each community, and the ecological and community changes that followed. It uses the two cases to illustrate how reinforcing cycles of decline can be redirected toward reinforcing cycles of recovery.

Overview: This article examines the restoration of mangrove forests and coastal fisheries in Trang Province, Thailand, as a case study of an Eco Tipping Point. It describes how commercial fishing, mangrove clearing, and declining fish stocks contributed to environmental degradation and economic pressures on coastal villages. The article then traces the development of community-managed mangrove forests, seagrass restoration, fishing restrictions, and other locally organized initiatives undertaken with support from Yadfon. It uses the changes that followed these efforts to illustrate the authors’ concept of shifting a community and its environment from a reinforcing cycle of decline toward a reinforcing cycle of recovery.

Overview: This article presents EcoTipping Points as a framework for teaching students about environmental problems and possible pathways toward restoration. It uses the recovery of the coral-reef fishery at Apo Island in the Philippines as its principal case study, tracing the decline of the fishery, creation of a marine sanctuary, changes in local fishing practices, and subsequent ecological and community developments. The article also describes other EcoTipping Points case studies and identifies recurring patterns of reinforcing cycles of environmental decline and recovery. It then examines ways educators have incorporated these concepts into science and social studies instruction, including case-study analysis, classroom activities, role-playing, and feedback-loop diagrams.