Complementary benefits of tourism and hunting to communal conservancies in Namibia

Tourism and hunting both generate substantial revenues for communities and private operators in Africa, but few studies have quantitatively examined the trade‐offs and synergies that may result from these two activities. We evaluated financial and in‐kind benefit streams from tourism and hunting on 77 communal conservancies in Namibia from 1998 to 2013, where community‐based wildlife conservation has been promoted as a land‐use that complements traditional subsistence agriculture. We used data collected annually for all communal conservancies to characterize whether benefits were derived from hunting or tourism. We classified these benefits into 3 broad classes and examined how benefits flowed to stakeholders within communities under the status quo and under a simulated ban on hunting. Across all conservancies, total benefits from hunting and tourism increased at roughly the same rate, although conservancies typically started generating benefits from hunting within 3 years of formation as opposed to after 6 years for tourism. Disaggregation of data revealed that the main benefits from hunting were income for conservancy management and food in the form of meat for the community at large. The majority of tourism benefits were salaried jobs at lodges. A simulated ban on trophy hunting significantly reduced the number of conservancies that could cover their operating costs, whereas eliminating income from tourism did not have as severe an effect. Given that the benefits generated from hunting and tourism typically begin at different times in a conservancy's life‐span (earlier vs. later, respectively) and flow to different segments of local communities, these 2 activities together may provide the greatest incentives for conservation on communal lands in Namibia. A singular focus on either hunting or tourism would reduce the value of wildlife as a competitive land‐use option and have grave repercussions for the viability of community‐based conservation efforts in Namibia, and possibly other parts of Africa.     

Community Conservation and the Future of Africa's Wildlife

Abstract: The term community-based conservation (CBC) refers to wildlife conservation efforts that involve rural people as an integral part of a wildlife conservation policy. The key elements of such programs are that local communities participate in resource planning and management and that they gain economically from wildlife utilization. In part, CBC is seen as an alternative to the more exclusionary protectionist policies of the past, which often alienated rural people from conservation efforts. The new approach acts to make rural people a constituency for wildlife and therefore active backers of wildlife protection. Africans, however, are struggling with severe social and economic problems such as poverty, long-standing economic stagnation, rapid population growth, and environmental deterioration. Because of the pressures that Africans face in making a living, the application of CBC may not occur as readily or as successfully as its advocates would hope. It may also be that the approach is being oversold. I use brief case studies from Madagascar, Ethiopia, Zimbabwe, and Swaziland to highlight the possible conflicts between rural people's economic needs and the implementation of community conservation. In addition, the CBC literature treats the role of protection vaguely, as it does the question of what might happen if CBC fails to achieve wildlife conservation goals. Community-based conservation is an obvious advance over past practices because of its inclusive philosophy, but if rural people accept CBC because of its economic benefits, they may reject it at some point in the future if a better economic alternative is presented. Thus, CBC programs can work to produce a better relationship between wildlife and people, but only a vast improvement in the lives of rural Africans will ultimately produce a more secure future for the continent's wildlife.     

Trophy Hunting and Wildlife Conservation in Zambia

For wildlife conservation to succeed in developing countries, people who live in or near protected areas must receive benefits that offset the costs of their reduced access to natural resources. International trophy hunting is currently generating significant economic benefits for residents of game management areas in Zambia. This has been made possible through a revolving fund and an administrative program that direct revenues from trophy hunting to local wildlife management and community development projects. Benefits might be enhanced by better biological information for management, greater local participation in the allocation and operation of hunting concessions, and the promotion of ecological and ethical standards for trophy hunting. An international system of certification for trophy hunting operations could foster these improvements.     

Role of Prices and Wealth in Consumer Demand for Bushmeat in Gabon, Central Africa

Abstract:  Unsustainable hunting of wildlife for food is often a more immediate and significant threat to the conservation of biological diversity in tropical forests than deforestation. Why people eat wildlife is debated. Some may eat bushmeat because they can afford it; others may eat it because it is familiar, traditional, confers prestige, tastes good, or adds variety. We completed a survey of 1208 rural and urban households in Gabon, Africa, in 2002–2003 to estimate the effect of wealth and prices on the consumption of wildlife and other sources of animal protein. Consumption of bushmeat, fish, chicken, and livestock increased with increasing household wealth, and as the price of these commodities rose, consumption declined. Although the prices of substitutes for bushmeat did not significantly, in statistical terms, influence bushmeat consumption, as the price of wildlife increased and its consumption fell, the consumption of fish rose, indicating that fish and bushmeat were dietary substitutes. Our results suggest that policy makers can use economic levers such as taxation or supply reduction through better law enforcement to change demand for wildlife. These measures will help to regulate unsustainable exploitation and reduce the risk of irreversible loss of large-bodied and slow-reproducing wildlife species. If policy makers focus solely on reducing the unsustainable consumption of wildlife, they may see adverse impacts on the exploitation of fish. Furthermore, policy makers must ensure that raising household wealth through development assistance does not result in undesirable impacts on the conservation status of wildlife and fish.     

Roads, Development, and Conservation in the Congo Basin

Abstract: Road density is closely linked to market accessibility, economic growth, natural resource exploitation, habitat fragmentation, deforestation, and the disappearance of wildlands and wildlife. Research in the Republic of Congo shows that roads established and maintained by logging concessions intensify bushmeat hunting by providing hunters greater access to relatively unexploited populations of forest wildlife and by lowering hunters' costs to transport bushmeat to market. Reconciling the contrary effects of roads on economic development and biodiversity conservation is one of the key challenges to wildlife managers in all nations. As the Democratic Republic of Congo prepares to reconstruct its almost completely collapsed road system, the government, donors, and conservation organizations have a unique opportunity to strategically prioritize investment in segments of the network that would maximize local and national economic benefits while minimizing adverse effects on forest wildlife.     

Economic Valuation of Subsistence Harvest of Wildlife in Madagascar

Wildlife consumption can be viewed as an ecosystem provisioning service (the production of a material good through ecological functioning) because of wildlife's ability to persist under sustainable levels of harvest. We used the case of wildlife harvest and consumption in northeastern Madagascar to identify the distribution of these services to local households and communities to further our understanding of local reliance on natural resources. We inferred these benefits from demand curves built with data on wildlife sales transactions. On average, the value of wildlife provisioning represented 57% of annual household cash income in local communities from the Makira Natural Park and Masoala National Park, and harvested areas produced an economic return of U.S.$0.42 ha^?1· year^?1. Variability in value of harvested wildlife was high among communities and households with an approximate 2 orders of magnitude difference in the proportional value of wildlife to household income. The imputed price of harvested wildlife and its consumption were strongly associated (p< 0.001), and increases in price led to reduced harvest for consumption. Heightened monitoring and enforcement of hunting could increase the costs of harvesting and thus elevate the price and reduce consumption of wildlife. Increased enforcement would therefore be beneficial to biodiversity conservation but could limit local people's food supply. Specifically, our results provide an estimate of the cost of offsetting economic losses to local populations from the enforcement of conservation policies. By explicitly estimating the welfare effects of consumed wildlife, our results may inform targeted interventions by public health and development specialists as they allocate sparse funds to support regions, households, or individuals most vulnerable to changes in access to wildlife. Valoración Económica de la Caza de Subsistencia de Vida Silvestre en Madagascar     

Transvalued Species in an African Forest

Abstract: We combined ethnographic investigations with repeated ecological transect surveys in the Dzanga‐Sangha Dense Forest Reserve (RDS), Central African Republic, to elucidate consequences of intensifying mixed use of forests. We devised a framework for transvaluation of wildlife species, which means the valuing of species on the basis of their ecological, economic, and symbolic roles in human lives. We measured responses to hunting, tourism, and conservation of two transvalued species in RDS: elephants (Loxodonta cyclotis) and gorillas (Gorilla gorilla). Our methods included collecting data on encounter rates and habitat use on line transects. We recorded cross‐cultural variation in ideas about and interactions with these species during participant observation of hunting and tourism encounters and ethnographic interviews with hunters, conservation staff, researchers, and tourists. Ecologically, gorillas used human‐modified landscapes successfully, and elephants were more vulnerable than gorillas to hunting. Economically, tourism and encounters with elephants and gorillas generated revenues and other benefits for local participants. Symbolically, transvaluation of species seemed to undergird competing institutions of forest management that could prove unsustainable. Nevertheless, transvaluation may also offer alternatives to existing social hierarchies, thereby integrating local and transnational support for conservation measures. The study of transvaluation requires attention to transnational flows of ideas and resources because they influence transspecies interactions. Cross‐disciplinary in nature, transvalution of species addresses the political and economic challenges to conservation because it recognizes the varied human communities that shape the survival of wildlife in a given site. Transvaluation of species could foster more socially inclusive management and monitoring approaches attuned to competing economic demands, specific species behaviors, and human practices at local scales.     

Human–wildlife coexistence in a changing world

Human–wildlife conflict (HWC) is a key topic in conservation and agricultural research. Decision makers need evidence-based information to design sustainable management plans and policy instruments. However, providing objective decision support can be challenging because realities and perceptions of human–wildlife interactions vary widely between and within rural, urban, and peri-urban areas. Land users who incur costs through wildlife argue that wildlife-related losses should be compensated and that prevention should be subsidized. Supporters of human–wildlife coexistence policies, such as urban-dwelling people, may not face threats to their livelihoods from wildlife. Such spatial heterogeneity in the cost and benefits of living with wildlife is germane in most contemporary societies. This Special Section features contributions on wildlife-induced damages that range from human perspectives (land use, psychology, governance, local attitudes and perceptions, costs and benefits, and HWC and coexistence theory) to ecological perspectives (animal behavior). Building on current literature and articles in this section, we developed a conceptual model to help frame HWC and coexistence dimensions. The framework can be used to determine damage prevention implementation levels and approaches to HWC resolution. Our synthesis revealed that inter- and transdisciplinary approaches and multilevel governance approaches can help stakeholders and institutions implement sustainable management strategies that promote human–wildlife coexistence.     

Bushmeat Supply and Consumption in a Tropical Logging Concession in Northern Congo

Abstract: Unsustainable hunting of wildlife for food empties tropical forests of many species critical to forest maintenance and livelihoods of forest people. Extractive industries, including logging, can accelerate exploitation of wildlife by opening forests to hunters and creating markets for bushmeat. We monitored human demographics, bushmeat supply in markets, and household bushmeat consumption in five logging towns in the northern Republic of Congo. Over 6 years we recorded 29,570 animals in town markets and collected 48,920 household meal records. Development of industrial logging operations led to a 69% increase in the population of logging towns and a 64% increase in bushmeat supply. The immigration of workers, jobseekers, and their families altered hunting patterns and was associated with increased use of wire snares and increased diversity in the species hunted and consumed. Immigrants hunted 72% of all bushmeat, which suggests the short‐term benefits of hunting accrue disproportionately to “outsiders” to the detriment of indigenous peoples who have prior, legitimate claims to wildlife resources. Our results suggest that the greatest threat of logging to biodiversity may be the permanent urbanization of frontier forests. Although enforcement of hunting laws and promotion of alternative sources of protein may help curb the pressure on wildlife, the best strategy for biodiversity conservation may be to keep saw mills and the towns that develop around them out of forests.     

Global justice and the opportunity costs of conservation

Opportunity costs can represent a significant portion of the costs associated with conservation projects and frequently outstrip other kinds of cost. They are typically understood to refer to the benefits someone would have obtained if conservation projects had not required them to give up current activities, such as farming or hunting or if the land had been available for uses other than conservation. This familiar way of identifying opportunity costs is flawed, however, because it threatens to condone, or take advantage of, the injustices that many people face that affect their opportunities. I integrated ideas from the political theory of global justice to examine how the analysis of opportunity costs illustrates the importance of considering conservation and issues of global justice together, rather than thinking about them in isolation. I distinguish four baselines for defining opportunity costs. A status quo baseline defines opportunity costs by asking what people would have earned had a conservation project not happened. A willingness to accept baseline defines them by asking people what it would take to make them indifferent to whether a conservation project takes place or not. An antipoverty baseline suggests that opportunity costs have been met when people affected by a project are not left in poverty. An egalitarian baseline suggests opportunity costs have been met when people are not left in relative disadvantage, with worse than average opportunities. I argue that the egalitarian baseline is the most acceptable from the point of view of justice. Such a baseline would suggest that, in practice, many of the world's poor are being unjustly treated, or even exploited, as a result of conservation activities.     

Application of the Anthropogenic Allee Effect Model to Trophy Hunting as a Conservation Tool

Trophy hunting can provide economic incentives to conserve wild species, but it can also involve risk when rare species are hunted. The anthropogenic Allee effect (AAE) is a conceptual model that seeks to explain how rarity may spread the seeds of further endangerment. The AAE model has increasingly been invoked in the context of trophy hunting, increasing concerns that such hunting may undermine rather than enhance conservation efforts. We question the appropriateness of uncritically applying the AAE model to trophy hunting for 4 reasons. First, the AAE assumes an open‐access resource, which is a poor characterization of most trophy‐hunting programs and obscures the potential for state, communal, or private‐property use rights to generate positive incentives for conservation. Second, study results that show the price of hunting increases as the rarity of the animal increases are insufficient to indicate the presence of AAE. Third, AAE ignores the existence of biological and behavioral factors operating in most trophy‐hunting contexts that tend to regulate the effect of hunting. We argue that site‐specific data, rather than aggregated hunting statistics, are required to demonstrate that patterns of unsustainable exploitation can be well explained by an AAE model. Instead, we suggest that conservation managers seeking to investigate and identify constraints that limit the potential conservation role of trophy hunting, should focus on the critical governance characteristics that shape the potential conservation role of trophy hunting, such as corruption, insecure property rights, and inadequate sharing of benefits with local people. Aplicación del Modelo Antropogénico del Efecto Allee sobre la Caza de Trofeos como una Herramienta de Conservación     

Addressing inequality and intolerance in human–wildlife coexistence

Millennia of human conflict with wildlife have built a culture of intolerance toward wildlife among some stakeholders. We explored 2 key obstacles to improved human–wildlife coexistence: coexistence inequality (how the costs and benefits of coexisting with wildlife are unequally shared) and intolerance. The costs of coexisting with wildlife are often disproportionately borne by the so-called global south and rural communities, and the benefits often flow to the global north and urban dwellers. Attitudes and behaviors toward wildlife (tolerance versus intolerance) vary with social and cultural norms. We suggest more empathetic advocacy is needed that, for example, promotes conservation while appropriately considering those who bear the costs of conflict with wildlife. To achieve more equitable cost-sharing, we suggest limiting the costs incurred by those most affected or by sharing those costs more widely. For example, we advocate for the development of improved wildlife compensation schemes, increasing the scale of rewilding efforts, and preventing wildlife-derived revenue leaching out of the local communities bearing the costs of coexistence.     

Trophy hunters’ willingness to pay for wildlife conservation and community benefits

In the face of fundamental land‐use changes, the potential for trophy hunting to contribute to conservation is increasingly recognized. Trophy hunting can, for example, provide economic incentives to protect wildlife populations and their habitat, but empirical studies on these relationships are few and tend to focus on the effects of benefit‐sharing schemes from an ex post perspective. We investigated the conditions under which trophy hunting could facilitate wildlife conservation in Ethiopia ex ante. We used a choice experiment approach to survey international trophy hunters’ (n = 224) preferences for trips to Ethiopia, here operationalized as trade‐offs between different attributes of a hunting package, as expressed through choices with an associated willingness to pay. Participants expressed strong preferences and, consequently, were willing to pay substantial premiums for hunting trips to areas with abundant nontarget wildlife where domestic livestock was absent and for arrangements that offered benefit sharing with local communities. For example, within the range of percentages considered in the survey, respondents were on average willing to pay an additional $3900 for every 10 percentage points of the revenue being given to local communities. By contrast, respondents were less supportive of hunting revenue being retained by governmental bodies: Willingness to pay decreased by $1900 for every 10 percentage points of the revenue given to government. Hunters’ preferences for such attributes of hunting trips differed depending on the degree to which they declared an interest in Ethiopian culture, nature conservation, or believed Ethiopia to be politically unstable. Overall, respondents thus expressly valued the outcomes of nature conservation activities—the presence of wildlife in hunting areas—and they were willing to pay for them. Our findings highlight the usefulness of insights from choice modeling for the design of wildlife management and conservation policies and suggest that trophy hunting in Ethiopia could generate substantially more financial support for conservation and be more in line with conservation objectives than is currently the case.     

Compensation for wildlife damages: Habitat conversion, species preservation and local welfare

We develop a model of hunting, farming and defensive action to study the environmental and economic consequences of introducing a program to compensate peasants of a small economy for the damage caused by wildlife. We show that the widespread belief that compensation induces wildlife conservation may be erroneous. Compensation can lower the wildlife stock, and may result in a net welfare loss for local people.     

Costs and Benefits of the Presence of Leopards to the Sport‐Hunting Industry and Local Communities in Niassa National Reserve,Mozambique

Sport hunting is often proposed as a tool to support the conservation of large carnivores. However, it is challenging to provide tangible economic benefits from this activity as an incentive for local people to conserve carnivores. We assessed economic gains from sport hunting and poaching of leopards (Panthera pardus), costs of leopard depredation of livestock, and attitudes of people toward leopards in Niassa National Reserve, Mozambique. We sent questionnaires to hunting concessionaires (n = 8) to investigate the economic value of and the relative importance of leopards relative to other key trophy‐hunted species. We asked villagers (n = 158) the number of and prices for leopards poached in the reserve and the number of goats depredated by leopard. Leopards were the mainstay of the hunting industry; a single animal was worth approximately U.S.$24,000. Most safari revenues are retained at national and international levels, but poached leopard are illegally traded locally for small amounts ($83). Leopards depredated 11 goats over 2 years in 2 of 4 surveyed villages resulting in losses of $440 to 6 households. People in these households had negative attitudes toward leopards. Although leopard sport hunting generates larger gross revenues than poaching, illegal hunting provides higher economic benefits for households involved in the activity. Sport‐hunting revenues did not compensate for the economic losses of livestock at the household level. On the basis of our results, we propose that poaching be reduced by increasing the costs of apprehension and that the economic benefits from leopard sport hunting be used to improve community livelihoods and provide incentives not to poach. Costos y Beneficios de la Presencia de Leopardos para la Industria de la Caza Deportiva y las Comunidades Locales en Niassa, Reserva Nacional, Mozambique     

A dynamic simulation model to support reduction in illegal trade within legal wildlife markets

Sustainable wildlife trade is critical for biodiversity conservation, livelihoods, and food security. Regulatory frameworks are needed to secure these diverse benefits of sustainable wildlife trade. However, regulations limiting trade can backfire, sparking illegal trade if demand is not met by legal trade alone. Assessing how regulations affect wildlife market participants’ incentives is key to controlling illegal trade. Although much research has assessed how incentives at both the harvester and consumer ends of markets are affected by regulations, little has been done to understand the incentives of traders (i.e., intermediaries). We built a dynamic simulation model to support reduction in illegal wildlife trade within legal markets by focusing on incentives traders face to trade legal or illegal products. We used an Approximate Bayesian Computation approach to infer illegal trading dynamics and parameters that might be unknown (e.g., price of illegal products). We showcased the utility of the approach with a small-scale fishery case study in Chile, where we disentangled within-year dynamics of legal and illegal trading and found that the majority (∼77%) of traded fish is illegal. We utilized the model to assess the effect of policy interventions to improve the fishery's sustainability and explore the trade-offs between ecological, economic, and social goals. Scenario simulations showed that even significant increases (over 200%) in parameters proxying for policy interventions enabled only moderate improvements in ecological and social sustainability of the fishery at substantial economic cost. These results expose how unbalanced trader incentives are toward trading illegal over legal products in this fishery. Our model provides a novel tool for promoting sustainable wildlife trade in data-limited settings, which explicitly considers traders as critical players in wildlife markets. Sustainable wildlife trade requires incentivizing legal over illegal wildlife trade and consideration of the social, ecological, and economic impacts of interventions.     

Impacts of hunting on tropical forests in Southeast Asia

Although deforestation and forest degradation have long been considered the most significant threats to tropical biodiversity, across Southeast Asia (Northeast India, Indochina, Sundaland, Philippines) substantial areas of natural habitat have few wild animals (>1 kg), bar a few hunting‐tolerant species. To document hunting impacts on vertebrate populations regionally, we conducted an extensive literature review, including papers in local journals and reports of governmental and nongovernmental agencies. Evidence from multiple sites indicated animal populations declined precipitously across the region since approximately 1980, and many species are now extirpated from substantial portions of their former ranges. Hunting is by far the greatest immediate threat to the survival of most of the region's endangered vertebrates. Causes of recent overhunting include improved access to forests and markets, improved hunting technology, and escalating demand for wild meat, wildlife‐derived medicinal products, and wild animals as pets. Although hunters often take common species, such as pigs or rats, for their own consumption, they take rarer species opportunistically and sell surplus meat and commercially valuable products. There is also widespread targeted hunting of high‐value species. Consequently, as currently practiced, hunting cannot be considered sustainable anywhere in the region, and in most places enforcement of protected‐area and protected‐species legislation is weak. The international community's focus on cross‐border trade fails to address overexploitation of wildlife because hunting and the sale of wild meat is largely a local issue and most of the harvest is consumed in villages, rural towns, and nearby cities. In addition to improved enforcement, efforts to engage hunters and manage wildlife populations through sustainable hunting practices are urgently needed. Unless there is a step change in efforts to reduce wildlife exploitation to sustainable levels, the region will likely lose most of its iconic species, and many others besides, within the next few years.     

Toward a new understanding of the links between poverty and illegal wildlife hunting

Conservation organizations have increasingly raised concerns about escalating rates of illegal hunting and trade in wildlife. Previous studies have concluded that people hunt illegally because they are financially poor or lack alternative livelihood strategies. However, there has been little attempt to develop a richer understanding of the motivations behind contemporary illegal wildlife hunting. As a first step, we reviewed the academic and policy literatures on poaching and illegal wildlife use and considered the meanings of poverty and the relative importance of structure and individual agency. We placed motivations for illegal wildlife hunting within the context of the complex history of how wildlife laws were initially designed and enforced to indicate how hunting practices by specific communities were criminalized. We also considered the nature of poverty and the reasons for economic deprivation in particular communities to indicate how particular understandings of poverty as material deprivation ultimately shape approaches to illegal wildlife hunting. We found there is a need for a much better understanding of what poverty is and what motivates people to hunt illegally.     

Using spatial patterns in illegal wildlife uses to reveal connections between subsistence hunting and trade

Although most often considered independently, subsistence hunting, domestic trade, and international trade as components of illegal wildlife use (IWU) may be spatially correlated. Understanding how and where subsistence and commercial uses may co‐occur has important implications for the design and implementation of effective conservation actions. We analyzed patterns in the joint geographical distribution of illegal commercial and subsistence use of multiple wildlife species in Venezuela and evaluated whether available data were sufficient to provide accurate estimates of the magnitude, scope, and detectability of IWU. We compiled records of illegal subsistence hunting and trade from several sources and fitted a random‐forest classification model to predict the spatial distribution of IWUs. From 1969 to 2014, 404 species and 8,340,921 specimens were involved in IWU, for a mean extraction rate of 185,354 individuals/year. Birds were the most speciose group involved (248 spp.), but reptiles had the highest extraction rates (126,414 individuals/year vs. 3,133 individuals/year for birds). Eighty‐eight percent of international trade records spatially overlapped with domestic trade, especially in the north and along the coast but also in western inland areas. The distribution of domestic trade was broadly distributed along roads, suggesting that domestic trade does not depend on large markets in cities. Seventeen percent of domestic trade records overlapped with subsistence hunting, but the spatial distribution of this overlap covered a much larger area than between commercial uses. Domestic trade seems to respond to demand from rural more than urban communities. Our approach will be useful for understanding how IWU works at national scales in other parts of the world.     

Rethinking the study of human–wildlife coexistence

Although coexistence with wildlife is a key goal of conservation, little is known about it or how to study it. By coexistence we mean a sustainable though dynamic state in which humans and wildlife coadapt to sharing landscapes, where human interactions with wildlife are effectively governed to ensure wildlife populations persist in socially legitimate ways that ensure tolerable risk levels. Problems that arise from current conflict-oriented framing of human–wildlife interactions include reinforcing a human–nature dichotomy as fundamentally oppositional, suggesting coexistence requires the absence of conflict, and skewing research and management toward direct negative impacts over indirect impacts and positive aspects of living with wildlife. Human behavior toward wildlife is framed as rational calculus of costs and benefits, sidelining emotional and cultural dimensions of these interactions. Coexistence is less studied due to unfamiliarity with relevant methodologies, including qualitative methods, self-reflexivity and ethical rigor, and constraints on funding and time. These challenges are illustrated with examples from fieldwork in India and Africa. We recommend a basic approach to case studies aimed at expanding the scope of inquiries into human–wildlife relations beyond studies of rational behavior and quantification of costs and benefits of wildlife to humans.