On the shoulders of some ecologists and conservation biologists rests the responsibility for guarding environmental systems from excessive abuse by humans. To this end, policy makers may be advised to introduce restrictions on behaviour of individuals and firms alike. Needless to say, such proposals often receive a hostile welcome, especially amongst private industries, where it is sometimes felt that ecologists overstate the importance of their case, proposing too stringent regulation too early and thereby causing excessive costs. Early signalling of resource depletion may be a rational (and indeed necessary) response by ecologists to the vagaries of policy making.

Whether market-oriented conservation, by which we mean the promotion of markets for the products of intact ecosystems, protects biodiversity, and under what conditions, has been a subject of much research and debate. Our evaluation of three strategies of the market-oriented use of natural resources led us to conclude that, at least for these three strategies, market-oriented mechanisms of conservation are often socially, economically, or ecologically unsustainable, and that proposals for market-oriented conservation should be approached with caution (Crook & Clapp 1998). Shackleton's (2001) critique and extension of the conditions for market-oriented conservation offers many useful insights, although we question some of his interpretations. Herein we examine some of those extensions, and revisit the criteria for successful market-oriented conservation.

In the north-western Peruvian Amazon, a new road has recently been constructed to link the city of Iquitos with the town of Nauta. The road crosses lands that are remarkably heterogeneous in terms of ecological conditions, comprising distinctive soil types from extremely poor to relatively fertile. Although this reality contributes to the land use potential and human carrying capacity of each place, deforestation of road margins appears equally intensive on all types of land. In the mid-1990s, two dead-end roads starting from both urban centres were characterized by distinctive zones of resource exploitation, with a road-free section of primary forest in between. A few years later, the separate road ends were linked by a dirt road that served only occasional traffic, but introduced significant new settlement. Various developmental trends evidence incoherent resource management and momentary public support in the region. By promoting diverse economic activities that reflect environmental conditions in the initial land use planning and land allocation, most sections along this road could be considered economically valuable for purposes such as sustainable forestry, tourism, agroforestry and, in suitable sites, intensive agriculture. To promote the more sustainable uses, thorough environmental legislation, administrative guidelines and follow-up based on an implicit mechanism of learning from previous experiences should be implemented. At the local level, there are some important initiatives to support such development, including ecological and economic zoning. However, these measures might be too late to prevent the destructive practices so common in many parts of Amazonia.

Protected area visitation is an important component of ecotourism, and as such, must be sustainable. However, protected area visitation may degrade natural resources, particularly in areas of concentrated visitor activities like trails and recreation sites. This is an important concern in ecotourism destinations such as Belize and Costa Rica, because they actively promote ecotourism and emphasize the pristine qualities of their natural resources. Research on visitor impacts to protected areas has many potential applications in protected area management, though it has not been widely applied in Central and South America. This study targeted this deficiency through manager interviews and evaluations of alternative impact assessment procedures at eight protected areas in Belize and Costa Rica. Impact assessment procedures included qualitative condition class systems, ratings systems, and measurement-based systems applied to trails and recreation sites. The resulting data characterize manager perceptions of impact problems, document trail and recreation site impacts, and provide examples of inexpensive, efficient and effective rapid impact assessment procedures. Interview subjects reported a variety of impacts affecting trails, recreation sites, wildlife, water, attraction features and other resources. Standardized assessment procedures were developed and applied to record trail and recreation site impacts. Impacts affecting the study areas included trail proliferation, erosion and widening, muddiness on trails, vegetation cover loss, soil and root exposure, and tree damage on recreation sites. The findings also illustrate the types of assessment data yielded by several alternative methods and demonstrate their utility to protected area managers. The need for additional rapid assessment procedures for wildlife, water, attraction feature and other resource impacts was also identified.

Increases in spiny lobster size and abundance have been observed within some marine protected areas (MPAs). To date, the potential economic benefits of these changes have been assumed to derive from the effects of emigration of adult lobster to adjacent fishing grounds and/or increased larval export to downstream nurseries that sustain fisheries. According to economic theory, these effects may provide consumptive (extractive) economic value to the fishery but are only part of the total economic value. Non-extractive economic value resulting from viewing wildlife may also have an important impact on the overall economic viability of some MPAs. This research examined scuba diver preferences in the Turks and Caicos Islands using a paired comparison conjoint survey and assessed the influence that spiny lobster (Panulirus argus) presence had on market share for dive charter packages of varying environmental quality and price. Market simulations showed significant increases in market share for dives where spiny lobsters were present, implying, for the first time, that spiny lobsters have non-extractive economic value. This non-extractive value of spiny lobster may have an important impact on the economic viability of some MPAs, especially those in regions like the Turks and Caicos Islands that are highly dependent on marine-oriented nature tourism.

Swine (Sus scrofa) have been introduced in many places throughout the world, and in many places they adversely affect the environment, economically impact agriculture, and/or harbour diseases transmittable to domestic livestock or humans. An easily applied method to assess their abundance is an important need for their management. To monitor efficacy of a swine control programme in Florida, data from passive tracking plots provide an index of feral swine abundance. The same track data coupled with plot locations to numerically describe the spatial pattern of swine activity gave an index of pervasiveness, and a simple rate of interception of damage sites to index damage was used. The assessments were conducted in January, May, and August 2000 in Jonathan Dickinson State Park, Florida, USA. Between the first two assessments a swine control programme removed 25 feral swine from the 8.3 km2 study area, after which the value of the passive tracking index was reduced by 81% and the fresh damage index by 89%, while the index of spatial pattern (pervasiveness index) showed only a small localized concentration after control. In the three months following the second assessment, Park personnel removed three additional swine from the study area, and a follow-up assessment indicated slightly less swine activity than immediately after the post-control assessment, however the index of pervasiveness showed a similar spatial pattern of activity as the initial assessment, possibly indicating re-invasive pressure. The passive tracking plots proved to be an uncomplicated, easily applied means to gather data for assessing and comparing swine abundance and distribution.

Recreational camping in wilderness areas causes a number of biophysical impacts, including loss of woody debris through campfires. Although extensive research has documented trampling impacts to vegetation, few studies have explored the extent of woody material depletion. This study adapted planar transect methods to measure the relative loss of fine (<0.6 cm), small (0.6 to 2.5 cm), medium (2.6 to 7.6 cm) and large (>7.6 cm) diameter materials in three concentric rings extending 0–5 m, 5–10 m and 10–15 m from the centre of 58 campsites in different environments ranging in elevation from 1250 to 2225 m in the Cascades Mountains in Oregon, USA. Compared to matched controls, losses were greatest for small (40%) and medium-sized (63%) materials, but were evident for fine (25%) and large (30%) materials as well. Surprisingly, depletion (across all sizes) was no greater in the centre of sites than in the outer measurement ring, even though the outer ring was often in intact vegetation. This suggests that impacts on woody debris extend beyond those impacts to vegetation typically monitored at campsites. Such recreational impacts to woody debris have rarely been systematically described. However, research on woody debris removal related to forest management indicates possible ecological effects of fuelwood consumption.

There has been a rapid expansion in the commercial cultivation of genetically modified crops, rising from the first plantings in 1995 to 44.5 million hectares worldwide in 2000, most of which have grown in North America. Though there are sharp divisions in opinions on benefits and risk, genetic modification (GM) does not represent a single, homogenous technology. Each application brings different potential benefits and risks for different stakeholders. This paper reviews recent scientific progress and future applications using a new typology of three generations of genetically modified organisms (GMOs) ranged against five types of scientific application. Agricultural GMOs pose a range of potential environmental and health risks. An analysis of recent independent field and scientific evidence from industrialized countries summarizes the current state of knowledge on seven types of risk that apply to all agricultural systems: (1) horizontal gene flow; (2) new forms of resistance and pest problems; (3) recombination to produce new pathogens; (4) direct and indirect effects of novel toxins; (5) loss of biodiversity from changes to farm practices; (6) allergenic and immune system reactions; and (7) antibiotic resistance marker genes. There remain highly contrasting positions taken by different stakeholders over GMOs. A review of three debates explains claims and counter-claims for (1) genetic modification as technological fix or contributor to sustainability; (2) genetic modification as driver of corporate power or friend of farmer; and (3) genetic modification as feeder of the world or eliminator of alternatives.

Animal tolerance to human approaches may be used to establish buffers for wildlife that can minimize the probability that animals will be disturbed by human activity. Alert distance (the distance between an animal and an approaching human at which point the animal begins to exhibit alert behaviours to the human) has been proposed as an indicator of tolerance mainly for waterbirds; however, little is known about its utility for other bird species. The factors that influenced alert distances of four bird species to pedestrian approaches in five large wooded fragments in the city of Madrid (Spain) were analysed. Location of human activity affected only Passer domesticus alert distances, which increased in the proximity of pathways. Habitat structure modified alert distances of all the species (Passer domesticus, Turdus merula, Columba palumbus, and Pica pica), increasing bird tolerance with greater availability of escape cover (shrub and coniferous cover, and shrub height). Alert distances varied among species, with large species being less tolerant of human disturbance than small ones. Alert distance appears to be a more conservative indicator of tolerance than flight distances, because it includes a buffer zone (the difference between alert and flight distance) in which birds may adapt their reaction to the behaviour of visitors. Alert distance may be used in the determination of minimum approaching areas, allowing people to enjoy their visit to parks, and birds to use patches for foraging and breeding without being displaced.

The hypothesis of attaching and realising market values as one means of conserving biodiversity has gained ground over the last decade. This has been challenged recently after examination of a number of case studies, largely from tropical Amazonia, on high value logging, marketing of non-timber forest products, and bioprospecting. The conclusion was that market-orientated conservation has seldom generated the financial returns envisaged, and as such cannot be used as an incentive to prevent land transformation. This paper reviews the basis of the challenge to market-orientated conservation on a number of grounds, drawing on examples largely from southern Africa. It concludes that generalizations from tropical Amazonia regarding the failure of market-orientated conservation are probably premature, and that it should remain an option, amongst a number of options, for conservation of biodiversity. Additionally, the prerequisite criteria identified as necessary to create an enabling framework for the success of market-orientated conservation are insufficient. Case studies are presented where the prerequisites do not apply, yet current extraction for market purposes is sustainable. Other potential prerequisites are also considered. There is a need for multivariate analysis, based on a large sample size drawn from across a range of environments and resources, of which factors are important prerequisites for successful market-orientated conservation, and under which circumstances.

High livestock densities in rangelands can result in reduced animal production due either to overgrazing or reduced per caput food availability, yet evidence for reduced animal production due to overstocking is scarce. Here simple animal production models establish the occurrence of overstocking in a traditional agropastoral system in the Spiti Valley of the Indian Trans-Himalaya. Empirical data show that fecundity of adult female livestock is related to total livestock biomass density (S) as a negative linear function of S. Total herd production is modelled as a quadratic function of S, thereby calculating an optimum livestock biomass density (Sop), at which total herd production is maximized. A sample of 40 villages showed that over 83% of Spiti's rangelands may be overstocked with values of S > Sop. Overstocking seems to be a classic case of the tragedy of the commons, as livestock is individually owned while the land is communally grazed. Recent socio-economic changes have probably contributed to high levels of overstocking. Even areas within wildlife reserves are overstocked. Conservation management needs to focus on creation of grazing free areas and management of livestock densities.