Paul R. Armsworth

Biodiversity and the Feel-Good Factor: Understanding Associations between Self-Reported Human Well-Being and Species Richness

Over half of the worlds human population lives in cities, and for many, urban greenspaces are the only places where they encounter biodiversity. This is of particular concern because there is growing evidence that human well-being is enhanced by exposure to nature. However, the specific qualities of greenspaces that offer the greatest benefits remain poorly understood. One possibility is that humans respond positively to increased levels of biodiversity. Here, we demonstrate the lack of a consistent relationship between actual plant, butterfly, and bird species richness and the psychological well-being of urban greenspace visitors. Instead, well-being shows a positive relationship with the richness that the greenspace users perceived to be present. One plausible explanation for this discrepancy, which we investigate, is that people generally have poor biodiversity-identification skills. The apparent importance of perceived species richness and the mismatch between reality and perception pose a serious challenge for aligning conservation and human well-being agendas.

The structure of reef fish metapopulations:modelling larval dispersal and retention patterns

An improved understanding of the dispersal patterns of marine organisms is a prerequisite for successful marine resource management. For species with dispersing larvae, regional–scale hydrodynamic models provide a means of obtaining results over relevant spatial and temporal scales. In an effort to better understand the role of the physical environment in dispersal, we simulated the transport of reef fish larvae among 321 reefs in and around the Cairns Section of the Great Barrier Reef Marine Park over a period of 20 years. Based on regional–scale hydrodynamics, our models predict the spatial and temporal frequency of significant self–recruitment of the larvae of certain species. Furthermore, the results suggest the importance of a select few local populations in ensuring the persistence of reef fish metapopulations over regional scales.

Biodiversity Conservation and the Millennium Development Goals

Any near-term gains in reducing extreme poverty will be maintained only if environmental sustainability is also achieved. The Millennium Development Goals (MDGs) are designed to inspire efforts to improve peoples lives by, among other priorities, halving extreme poverty by 2015 (1). Analogously, concern about global decline in biodiversity and degradation of ecosystem services (2) gave rise in 1992 to the Convention on Biological Diversity (CBD). The CBD target “to achieve by 2010 a significant reduction of the current rate of biodiversity loss” was incorporated into the MDGs in 2002. Our lack of progress toward the 2010 target (3, 4) could undermine achievement of the MDGs and poverty reduction in the long term. With increasing global challenges, such as population growth, climate change, and overconsumption of ecosystem services, we need further integration of the poverty alleviation and biodiversity conservation agendas.

RECRUITMENT LIMITATION, POPULATION REGULATION, AND LARVAL CONNECTIVITY IN REEF FISH METAPOPULATIONS

Two central debates in marine ecology concern the role of connectivity patterns via larval dispersal in structuring marine metapopulations and the relative importance of larval supply vs. events occurring during or after settlement in determining adult abundance. Both issues were examined using age-structured models and simulations of reef fish population dynamics at the regional scale of closed metapopulations and the local scale of individual reefs. Local populations on individual reefs were assumed to be at once both partially open and partially closed. Two sets of models over both spatial scales are presented. One set examines density-independent dynamics. In the other set, mortality in the first year depends on the density of the settling cohort, and the density dependence is compensatory. The sensitivities of local population dynamics to the rates of self-recruitment and external larval supply were predicted. If external larval supply is regular and there is little self-recruitment, then a local population can appear to be regulated without conventional forms of density dependence. Elsewhere, this process has been termed “recruitment regulation.” However, with increased self-recruitment a local population will grow without bound in the absence of regulatory density dependence. Metapopulation persistence requires a sufficiently strong linkage between stock and recruitment in some local population. In such a local population, individuals must contribute sufficiently many offspring to replace themselves locally in subsequent generations. Such a local population could either be partially closed or lie in a region of the metapopulation that is strongly interconnected. Metapopulation regulation requires that density dependence acts to curb population growth in local source populations but does not require that it acts in local sink populations. The density dependence need not be so strong as to prevent subsequent cohort sizes from correlating well with varying recruitment levels. Recruitment regulation alone cannot regulate a metapopulation. Two versions of the recruitment limitation hypothesis were examined. The first version states that varying recruitment levels are good predictors of subsequent population size; the second version states that postrecruitment demographic rates are density independent. The present models, along with a growing body of empirical data, support the first hypothesis but provide less support for the second one. Population regulation and the first form of recruitment limitation are not antithetical processes.

The Impact of Directed versus Random Movement on Population Dynamics and Biodiversity Patterns

An improved understanding of dispersal behavior is needed to predict how populations and communities respond to habitat fragmentation. Most spatial dynamic theory concentrates on random dispersal, in which movement rates depend neither on the state of an individual nor its environment and movement directions are unbiased. We examine the neglected dispersal component of directed movement in which dispersal is a conditional and directional response of individuals to varying environmental conditions. Specifically, we assume that individuals bias their movements along local gradients in fitness. Random movers, unable to track heterogeneous environmental conditions, face source‐sink dynamics, which can result in deterministic extinction or increase their vulnerability to stochastic extinction. Directed movers track environmental conditions closely. In fluctuating environments, random movers “spread their bets” across patches, while directed movers invest offspring in habitats currently enjoying propitious conditions. The autocorrelation in the environment determines each strategy’s success. Random movers permeate entire landscapes, but directed movers are more geographically constrained. Local information constraints limit the ranges of directed movers and introduce a role for historical contingency in determining their ultimate distribution. These geographic differences have implications for biodiversity. Random movement maintains biodiversity through local coexistence, but directed movement favors a spatial partitioning of species.

Ecosystem-service science and the way forward for conservation.

Conservation biology began life as a crisis discipline, its central tenet to understand and help reverse losses of biodiversity and habitat. Those losses continue unabated, implying that, as a discipline, we are failing in our central charge. A growing number of conservation biologists are therefore looking for a new way forward, and we believe that an increased focus on ecosystem services provides it. Yet the conservation community remains deeply, and sometimes very publicly (McCauley 2006), divided over how much emphasis ecosystem-service approaches should receive relative to those based solely on moral suasion. Put bluntly, will we achieve greater conservation success by protecting nature for its own sake or for our own sake? This dichotomy highlights extremes of a continuum that was prominent a century ago. Nature for nature’s sake, often blended with aesthetic appeals, can be traced most notably to the preservationist John Muir. Conservation through utilization can be traced to another icon, forester Gifford Pinchot. These complementary strands, each valid, powerful, and deeply rooted in the conservation movement, clashed long ago, especially in the United States. But just as Muir’s writings acknowledge a role for utilitarianism and Pinchot’s a keen awareness of the intrinsic value of nature, pluralism between the two schools of thought is the norm in conservation practice. For example, in a survey of current projects underway in major conservation nongovernmental organizations, it is proving difficult to distinguish those focused on biodiversity for its own sake and those focused on ecosystem services and human well-being. Most projects mix the two approaches, drawing on the diverse ways in which people perceive and interact with nature to motivate action. We see an expanded role for ecosystem-service approaches in conservation not because these approaches are more valid in some way, but because they have not yet come close to reaching their conservation potential and because people from all walks of life can contribute to the realization of that potential. Despite past successes, the rate of biodiversity loss has not slackened, making it urgent that we broaden and strengthen the foundation for conservation. Nature for nature’s sake resonates only with the already converted. Business interests, farmers, and the billion humans living in rural poverty remain unwilling or unable to move. We need these people as partners in conservation, and ecosystem-service approaches provide a means of motivating and enabling them. If human dependence on nature becomes widely recognized, society will demand greater environmental stewardship. The resulting investments in conservation promise to outweigh select instances in which the two approaches conflict. Arguing for a greater focus on ecosystem services is not “selling out” biodiversity (McCauley 2006)—quite the opposite. By emphasizing the many ways nature sustains and enriches people’s everyday lives, ecosystem-service programs turn traditional conservation approaches, which are based on separating people from nature, on their heads. Conservation efforts premised on protecting a small number of places or species from people are necessary but far from sufficient. Conservation efforts must be interwoven throughout entire land and seascapes and must place greater emphasis on preserving population numbers and diversity if they are to sustain biodiversity. Arguments for ecosystem-service approaches drive us toward this vision of conservation. Already, ecosystem-service advocates are finding allies and enjoying traction in places where ethical arguments for biodiversity conservation are given short shrift. For example, ecosystem-service ideas embed concerns about the environment and biodiversity in the heart of broader policy debates concerning global poverty reduction (Sachs & Reid 2006). In much of the world, conserving nature out of moral obligation is a luxury most simply cannot afford. Nevertheless, human well-being is intimately linked to the immediate environment and natural capital is a vital part of the economic base. In the face of a sea of poverty, demonstrating the ignored links between nature and elements of well-being—safe drinking water, food, fuel, flood control, and aesthetic and cultural benefits that contribute to dignity and satisfaction—is the key to making conservation relevant and, if we are lucky, possible. As a community conservation biologists must refocus research efforts to deliver the science to support ecosystem-service conservation. The Millennium

The impact of projected increases in urbanization on ecosystem services

Alteration in land use is likely to be a major driver of changes in the distribution of ecosystem services before 2050. In Europe, urbanization will probably be the main cause of land-use change. This increase in urbanization will result in spatial shifts in both supplies of ecosystem services and the beneficiaries of those services; the net outcome of such shifts remains to be determined. Here, we model changes in urban land cover in Britain based on large (16%) projected increases in the human population by 2031, and the consequences for three different services—flood mitigation, agricultural production and carbon storage. We show that under a scenario of densification of urban areas, the combined effect of increasing population and loss of permeable surfaces is likely to result in 1.7 million people living within 1 km of rivers with at least 10 per cent increases in projected peak flows, but that increasing suburban ‘sprawl’ will have little effect on flood mitigation services. Conversely, losses of stored carbon and agricultural production are over three times as high under the sprawl as under the ‘densification’ urban growth scenarios. Our results illustrate the challenges of meeting, but also of predicting, future demands and patterns of ecosystem services in the face of increasing urbanization.

Balancing alternative land uses in conservation prioritization

Pressure on ecosystems to provide various different and often conflicting services is immense and likely to increase. The impacts and success of conservation prioritization will be enhanced if the needs of competing land uses are recognized at the planning stage. We develop such methods and illustrate them with data about competing land uses in Great Britain, with the aim of developing a conservation priority ranking that balances between needs of biodiversity conservation, carbon storage, agricultural value, and urban development potential. While both carbon stocks and biodiversity are desirable features from the point of view of conservation, they compete with the needs of agriculture and urban development. In Britain the greatest conflicts exist between biodiversity and urban areas, while the largest carbon stocks occur mostly in Scotland in areas with low agricultural or urban pressure. In our application, we were able successfully to balance the spatial allocation of alternative land uses so that conflicts between them were much smaller than had they been developed separately. The proposed methods and software, Zonation, are applicable to structurally similar prioritization problems globally.

Ecosystem service benefits of contrasting conservation strategies in a human-dominated region

The hope among policy-makers and scientists alike is that conservation strategies designed to protect biodiversity also provide direct benefits to people by protecting other vital ecosystem services. The few studies that have examined the delivery of ecosystem services by existing conservation efforts have concentrated on large, ‘wilderness’-style biodiversity reserves. However, such reserves are not realistic options for densely populated regions. Here, we provide the first analyses that compare representation of biodiversity and three other ecosystem services across several contrasting conservation strategies in a human-dominated landscape (England). We show that small protected areas and protected landscapes (restrictive zoning) deliver high carbon storage and biodiversity, while existing incentive payment (agri-environment) schemes target areas that offer little advantage over other parts of England in terms of biodiversity, carbon storage and agricultural production. A fourth ecosystem service—recreation—is under-represented by all three strategies. Our findings are encouraging as they illustrate that restrictive zoning can play a major role in protecting natural capital assets in densely populated regions. However, trade-offs exist even among the four ecosystem services we considered, suggesting that a portfolio of conservation and sustainability investments will be needed to deliver both biodiversity and the other ecosystem services demanded by society.

Reconciling biodiversity and carbon conservation

Climate change is leading to the development of land-based mitigation and adaptation strategies that are likely to have substantial impacts on global biodiversity. Of these, approaches to maintain carbon within existing natural ecosystems could have particularly large benefits for biodiversity. However, the geographical distributions of terrestrial carbon stocks and biodiversity differ. Using conservation planning analyses for the New World and Britain, we conclude that a carbon-only strategy would not be effective at conserving biodiversity, as have previous studies. Nonetheless, we find that a combined carbon-biodiversity strategy could simultaneously protect 90% of carbon stocks (relative to a carbon-only conservation strategy) and > 90% of the biodiversity (relative to a biodiversity-only strategy) in both regions. This combined approach encapsulates the principle of complementarity, whereby locations that contain different sets of species are prioritised, and hence disproportionately safeguard localised species that are not protected effectively by carbon-only strategies. It is efficient because localised species are concentrated into small parts of the terrestrial land surface, whereas carbon is somewhat more evenly distributed; and carbon stocks protected in one location are equivalent to those protected elsewhere. Efficient compromises can only be achieved when biodiversity and carbon are incorporated together within a spatial planning process.