Jeffrey A. Lockwood

Catastrophic Thresholds: A Synthesis of Concepts, Perspectives, and Applications

Research reported in this feature identifies a convergence of interpretations regarding the threshold dynamics of complex ecological systems. This convergence has arisen from a diverse set of investigations addressing rangeland ecosystem dynamics, disease transmission, and fluctuations in the populations of insect pests. Effective application of the threshold concept to ecosystem management will require development of more robust linkages between non-equilibrium theory and protocols to identify triggers that initiate threshold conditions, feedback loops that establish system resilience, and developmental trajectories and attributes of potential alternative stable states. Successful implementation of these theory/ application linkages has the potential to underpin an operational framework of resilience-based ecosystem management that is founded upon the identification of structural indicators that are correlated with vulnerability or proximity to thresholds, rather than threshold identification per se. Several investigations indicate that thresholds are strongly influenced by scale; multiple cross-scale interactions demonstrate the need for greater knowledge and analyses to address scale-dependent processes, i.e., critical scales and scaling laws. This feature emphasizes the relevance of thresholds and non-equilibrium dynamics in multiple natural resource management applications and in so doing demonstrates the need for a more comprehensive and integrated ecological framework capable of quantitatively assessing dynamics at multiple scales to inform management and policy recommendations for optimal management and risk assessment.

Agriculture and biodiversity: Finding our place in this world

Agriculture has been recently viewed as the primary destructive force of biodiversity, but the places that produce our food and fiber may also hold the key to saving the richness of life on earth. This argument is based on three fundamental positions. First, it is argued that to value and thereby preserve and restore biodiversity we must begin by employing anthropocentric ethics. While changing our understanding of intrinsic values (i.e., the unconditional values of biodiversity as a state and process in-and-of-itself, without reference to human interests) is often advocated as the means by which our behavior will reflect the importance of biodiversity, a change in how we perceive and conditionally value biodiversity is proposed as a more effective and compelling approach. Second, I suggest that anthropocentric values can be linked to a sense of “Place,” with agriculture playing a vital role in this context. Agriculture forms a powerful basis for personal, experiential development of a profound meaning and connection to a setting or landscape. The agricultural setting has tremendous potential for arational (emotional, aesthetic, and spiritual) values that ultimately compel our actions. The constancy of relationship and mutuality of dependency between humans and agricultural lands, particularly extensive agroecosystems, fosters an intensity of association that transcends our recent affinity to wildlands. Third, a mature understanding of places and their biodiversity must include those organisms that account for many of the ecological processes and the majority of the species richness -- the insects. The importance of these insects in structuring the landscape and the effects of habitat destruction on these organisms both suggest a vital, intimate, and reciprocal link between insects and Places. Finally, it is argued that the most important avenue for future efforts to protect and restore biodiversity on the part of agricultural and other scientists is educational -- the presentation of our research to the public in terms that provoke emotional, aesthetic, and spiritual meaning which lies at the core of human values and actions.

Decreasing Economic and Environmental Costs through Reduced Area and Agent Insecticide Treatments (RAATs) for the Control of Rangeland Grasshoppers: Empirical Results and Their Implications for Pest Management

-Reduced area and agent treatments (RAATs) for management of rangeland grasshopper infestations were compared with blanket applications of 2 standard compounds at traditional rates (100% of infestations treated with carbaryl applied at 16 oz/ac or malathion applied at 8 oz/ac) in southeastern Wyoming during 1995-96. Two RAATs applications of carbaryl (12 oz/ac applied in alternating swaths to 66% of infestations [12-66] and 8 oz/ac applied in alternating swaths to 50% of infestations [8-50]) were essentially indistinguishable from the standard treatment, with 80 to 90% grasshopper mortality. A carbaryl 8-33 treatment resulted in only 40 to 60% control. Mortality following application of 4 oz/ac of malathion in alternating swaths to 80% of an infestation (4-80) was indistinguishable from the standard application, with 75 to 90% control. However, a malathion 4-50 treatment resulted in only 55 to 65% control. Fipronil (14 oz/ac) applied to 25% of an infestation resulted in 80 to 90% control, comparable to the highest rates of mortality with the other RAATs. The greatest benefit: cost ratios (>2.8: 1) were seen with the carbaryl 8-50, malathion 4-80, and fipronil 14-25 treatments. The RAATs strategy appears to depend on movement of grasshoppers from untreated to treated swaths and on the conservation of natural biological control agents. Had RAATs methods been used during the 1986-88 outbreak in the western US, pest managers would have saved

The ethics of biological control: Understanding the moral implications of our most powerful ecological technology

38 million and used 34 million metric tons less insecticide [

Orthoptera conservation: pests and paradoxes

A system of environmental ethics recently developed by Lawrence Johnson may be used to analyze the moral implications of biological control. According to this system, entities are morally relevant when they possess well-being interests (i.e., functions or processes that can be better or worse in so far as the entity is concerned). In this formulation of ethical analysis, species and ecosystems are morally relevant because they are not simply aggregates of individuals, so their processes, properties, and well-being interests are not reducible to the sum of their individual members. Following Johnsons thesis, species and ecosystems have morally relevant interests in surviving and maintaining themselves as integrated wholes with particular self-identities. This theoretical structure gives rise to a number of ethical criteria that are particularly relevant to biological control, which apply to the ecosystem (the extent to which it is large, native, unique, and integrated) and to the action being considered (the extent to which it is novel, omnipresent, monitored, reversible, and necessary). In these terms, it is evident that not all biological control efforts are ethically defensible. In general terms, natural biological control is most desirable, followed by augmentative strategies, classical approaches, and finally neoclassical biological control. Two specific cases (neoclassical biological control of rangeland grasshoppers and classical biological control of prickly pear cactus) illustrate the ethical concerns. Finally, it can be shown that formalized restrictions of biological control are necessary, given the unique properties of this technology

The History of Biological Control with Nosema locustae : Lessons for Locust Management

Orthoptera species and assemblages vary enormously in biology, abundance, population variability and geographic range. This means that some are major pests but others are threatened with extinction or are extinct through human agency. Most pest species are in the Acrididae, yet proportionately more threatened species are in the less speciose families. Pest Orthoptera species are unusual on islands, which nevertheless support several threatened non-acridid species. In contrast, continental species of Acrididae and Tettigoniidae are the ones principally threatened. Many of the threatened Orthoptera species are confined to a small geographical area and are highly threatened by anthropogenic impacts that coincide with their small ranges. Yet some formerly widespread pest taxa have become extinct. Genetic polymorphism to a solitary phase appears to be an extinction-avoidance mechanism. While ‘classically’ threatened point endemics can receive conservation action, not much can be done for the periodically at risk abundant species. Preservation of orthopteran biodiversity is a complex and paradoxical task.

Olfactory basis of cannibalism in grasshoppers (Orthoptera: Acrididae): II. field assessment of attractants.

The historical account of the rise and fall of Nosema locustae as a biological control agent of grasshoppers has substantial implications for the successful development and implementation of biological control of migratory locusts in Africa. The potential of N. locustae was ultimately not sufficient to overcome a set of impediments, including: efficacy (the rate and extent of mortality were relatively low), target specificity (not all pest species were susceptible), formulation (wheat bran bait excluded feeding by some pests), cost (the price of the formulated product was excessive), storage (the organism lacked long-term stability), complex application (the pathogen and its carrier had to be applied during a narrow set of environmental and logistical parameters) and production (the use of an in vivo production system made high-volume production difficult). Some of the most significant limitations that led to the failure of N. locustae have been overcome by work on other pathogens, including the problems of formulation, storage, efficacy and production. However, at least four relevant lessons can be derived from the N. locustae story and applied to ongoing work with biological control of migratory locusts. First, the erratic population dynamics of acridids necessitates that the production, storage and distribution of an augmentative biological control agent will be driven by a boom-and-bust cycle. Second, the immense spatial scale and low unit value of the resources (rangelands) being protected create a unique set of logistical challenges. Third, the control of acridids involves the management of a native insect pest embedded within complex, native ecosystems, which suggests that our interventions should be undertaken with a great deal of caution, monitoring and, ultimately, humility. Fourth, although pathogens can be used as ‘bio-insecticides’, biological control requires education of end-users regarding a more sophisticated approach to pest management.RésuméLe bilan des forces et faiblesses des formulations à base de Nosema locustae comme agent biologique de lutte contre les criquets migratoires comporte des implications substantielles pour le développement efficace et la mise sur pied des méthodes de lutte contre les criquets migratoires en Afrique. En fin de compte, les potentialités de N. locustae n’ont pas été suffisantes pour parier une série d’obstacles dont: l’efficacité (la proportion et le spectre de mortalité sont restés relativement bas), la spécificité pour l’agent cible (toutes les espèces ne sont pas sensibles), la formulation (certaines espèces refusent de se nourrir sur les appâts à base de son de blé), le coût (coût très élevé pour la formulation), le stockage (instabilité à long terme du pouvoir pathogène de l’agent), la complication lors des traitements (l’agent biologique et les adjuvants doivent être appliqués dans des conditions rigoureuses incluant une série de paramètres environnementaux et logistiques), et enfin la production (la formulation du produit, in vitro, enfreint sa production à grande échelle). Certaines des contraintes les plus importantes conduisant aux échecs d’utilisation de N. locustae ont étaient surmontées grâce aux travaux menés chez d’autres pathogènes sur les problèmes de formulation, de stockage, d’efficacité et de production. Quatre leçons importantes peuvent cependant être dégagées de l’historique d’utilisation de N. locustae et appliquées aux travaux en cours sur les criquets migratoires. Primo, la dynamique de populations erratiques d’acridiens exige que la production, le stockage et la distribution d’un agent biologique supplémentaire soient orientés par le principe de cyclicité d’explosion et expension des fléaux. Secundo, les immenses étendues d’espace à traiter et la valeur unitaire insignifiante des ressources à protéger (pâturages) créent une série de défis logistiques à lever. Tertio, la lutte anti-acridienne visant une gestion d’un insecte autochtone faisant partie d’un complexe d’une faune endémique devrait s’effectuer avec une grande précaution et un suivi extrêmement minutieux. Quarto, quand bien même les agents biologiques peuvent être utilisés comme des bio-insecticides, la lutte biologique implique une formation des utilisateurs finaux compte tenu de son approche plus sophistiquée pour le contrôle du ravageur.

Nontarget Effects of Biological Control: What are We Trying to Miss?

The responses of rangeland grasshoppers to biologically and historically derived attractants were studied in a shortgrass prairie in southeastern Wyoming in July 1990. Seven long-chain fatty acids (C14–C20: singly and in combination), grasshopper cadavers, molasses, fruit extracts, and chloroform (solvent control) were tested. Each attractant was applied to filter paper and placed in an arena delimited by a 0.10-m2 aluminum ring. Grasshoppers were most attracted to linoleic and linolenic acids, with significantly more grasshoppers found in these arenas than in those of the controls or other attractants. These two fatty acids alone and in combination were more attractive at 1 grasshopper equivalent (GE) than at 5 GE. The seed bug,Lygaeus kalmii Stål, and five species of ants were also attracted to these two fatty acids. Molasses had significantly more grasshoppers on the filter paper than did the other attractants, but molasses had significantly fewer grasshoppers in the arena than the fatty acids. Fruit extracts were not effective at attracting grasshoppers. Water extracts of cadavers attracted significantly more grasshoppers to the bait than did chloroform extracts. Because the assayed grasshopper community was dominated by the Gomphocerinae (a subfamily that includes many pest species that do not readily consume wheat bran bait), it may be possible to use fatty acids in conjunction with insecticidal bran baits for increased control of rangeland grasshoppers.

Arthropod Prey‐Predator Ratios in a Sagebrush Habitat: Methodological and Ecological Implications

The history of pest management in general (Perkins 1982), and biological control in particular (Coppel and Mertins 1977, Caltagirone 1981, Goeden 1988, Van Driesche and Bellows 1996), has been thoroughly analyzed in terms of the dominant practices and how these actions relate to competing philosophies of ecological intervention (e.g., integrated vs. total pest management). While it is evident how environmentalism, as a social phenomenon, has altered the forms and concepts of pest management, it is not so clear how ecology, as a scientific discipline, might change the field of pest management. A great deal of work has been dedicated to the notion of “nontarget” effects, particularly as they relate to chemical control methods, but only recently have we begun to critically assess what exactly constitutes a “nontarget.” From a simple perspective this would seem to be self-evident—all organisms other than the pest are nontargets. However, this tautological approach does little to advance the science of pest management, and it is clear that in practice, the nature of the targets and nontargets is far from simple. The (re)conceptualization of the target can lead to important changes in pest management (e.g., defining the target based on an economic threshold, USDA 1996). Extending these principles to our understanding of nontargets promises to open new avenues for monitoring and protecting those elements that we wish to protect from the hazards of pest management practices in general, and biological control in particular.

Grasshoppers (Orthoptera: Acrididae) Could Serve as Reservoirs and Vectors of Vesicular Stomatitis Virus

A 3-yr study of arthropod prey-predator ratios, based on species richness and density, was conducted in undisturbed and in intensively managed sagebrush habitats in southeastern Wyoming. Using simulated data sets, Bartletts regression generated sig- nificantly more accurate prey-predator ratios than either simple ratios or ordinary least squares, so Bartletts regression was used for analysis of field data. Both richness and density ratios were generally constant across taxonomic groups (insects, arachnids, and all arthro- pods) in both undisturbed and managed habitats. Prey-predator richness ratios ranged from 1.18 to 2.36 and were considered temporally and spatially constant in undisturbed habitats. The more sensitive density ratios ranged from 2.23 to 7.77, and showed significant variation in time and space. Herbicide application significantly decreased the prey-predator richness ratios in the treatment year, but the ratios increased the following year. Mowing also decreased richness ratios, but the changes were not significant. Although spatial and temporal heterogeneity prevented determination of valid control for assessing the impact of disturbances on most density ratios, the management practices appeared to have in- creased prey-predator ratios in the treatment and posttreatment years.