Search

Avoiding catastrophic climate change requires rapid decarbonization and improved ecosystem stewardship at a planetary scale. The carbon released through the burning of fossil fuels would take millennia to regenerate on Earth. Though the timeframe of carbon recovery for ecosystems such as peatlands, mangroves and old-growth forests is shorter (centuries), this timeframe still exceeds the time we have remaining to avoid the worst impacts of global warming. There are some natural places that we cannot afford to lose due to their irreplaceable carbon reserves. Here we map ‘irrecoverable carbon’ globally to identify ecosystem carbon that remains within human purview to manage and, if lost, could not be recovered by mid-century, by when we need to reach net-zero emissions to avoid the worst climate impacts. Since 2010, agriculture, logging and wildfire have caused emissions of at least 4.0 Gt of irrecoverable carbon. The world’s remaining 139.1 ± 443.6 Gt of irrecoverable carbon faces risks from land-use conversion and climate change. These risks can be reduced through proactive protection and adaptive management. Currently, 23.0% of irrecoverable carbon is within protected areas and 33.6% is managed by Indigenous peoples and local communities. Half of Earth’s irrecoverable carbon is concentrated on just 3.3% of its land, highlighting opportunities for targeted efforts to increase global climate security. Avoiding catastrophic climate change requires that we avoid losing key natural carbon reserves. This study maps such irrecoverable carbon globally and finds a third of the remaining managed by Indigenous peoples and local communities and nearly a quarter in protected areas.

Non-technical summary Implicit in the UN's Sustainable Development Goal (SDG) Agenda is the notion that environmental sustainability is intertwined with, and underpins, the 17 Goals. Yet the language of the Goals, and their Targets and indicators is blind to the myriad ways in which nature supports people's health and wealth – which we argue represents a key impediment to progress. Using examples of nature–human wellbeing linkages, we assess the language of all 169 Targets to identify urgent research, policy, and action needed to spotlight and leverage nature's foundational role, to help enable truly sustainable development for all. Technical summary Nature's foundational role in helping achieve the SDGs is implicit rather than explicit in the language of SDGs Goals, Targets, and indicators. Drawing from the scientific literature describing how nature underpins human wellbeing, we carry out a systematic assessment of the language of all 169 Targets, categorizing which Targets are dependent upon nature for their achievement, could harm nature if attained through business-as-usual actions, or may synergistically benefit nature through their attainment. We find that half are dependent upon nature for their achievement – yet for more than two-thirds of those nature's role goes unstated and risks being downplayed or ignored. Moreover, while achieving the overwhelming majority of the 169 Targets could potentially benefit nature, more than 60% are likely to deliver ‘mixed outcomes’ – benefitting or harming nature depending on how they're achieved. Furthermore, of the 241 official indicators Social media summary Harmonizing links between the SDGs and the CBD's post-2020 Global Biodiversity Framework is vital for promoting sustainable development

Sustaining the organisms, ecosystems, and processes that underpin human well-being is necessary to achieve sustainable development. Here we analyze 14 of nature’s contributions to people (NCP) for food, water, and climate security. Using spatial optimization, we identify critical natural assets, the most important ecosystems for providing NCP, comprising 30% (for local benefits) to 44% (for local and global benefits) of total global land area and 24% of national territorial waters. Many of these NCP are left out of international agreements focused on conserving species or mitigating climate change, yet our analysis shows that explicitly prioritizing critical natural assets jointly advances development, climate, and conservation goals. Crafting policy and investment strategies that protect critical natural assets is essential for sustaining human well-being and securing Earth’s life support systems.

Avoiding catastrophic climate change requires rapid decarbonization and improved ecosystem stewardship. To achieve the latter, ecosystems should be prioritized by responsiveness to direct, localized action and the magnitude and recoverability of their carbon stores. Here, we show that a range of ecosystems contain ‘irrecoverable carbon’ that is vulnerable to release upon land use conversion and, once lost, is not recoverable on timescales relevant to avoiding dangerous climate impacts. Globally, ecosystems highly affected by human land-use decisions contain at least 260 Gt of irrecoverable carbon, with particularly high densities in peatlands, mangroves, old-growth forests and marshes. To achieve climate goals, we must safeguard these irrecoverable carbon pools through an expanded set of policy and finance strategies. In order to limit warming and the most severe consequences of climate change, net global carbon emissions must reach zero by 2050. Many ecosystems contain carbon that would be irrecoverable on this timescale if lost and must be protected to meet climate goals.

Sustaining the organisms, ecosystems, and processes that underpin human well-being is necessary to achieve sustainable development. Here we identify critical natural assets, natural and semi-natural ecosystems that provide 90% of the total current magnitude of 14 types of nature’s contributions to people (NCP). Critical natural assets for maintaining local-scale NCP (12 of the 14 NCP mapped) comprise 30% of total global land area and 24% of national territorial waters, while 44% of land area is required for maintaining all NCP (including those that accrue at the global scale, carbon storage and moisture recycling). At least 87% of the world’s population lives in the areas benefiting from critical natural assets for local-scale NCP, while only 16% lives on the lands containing these assets. Critical natural assets also overlap substantially with areas important for biodiversity (covering area requirements for 73% of birds and 66% of mammals) and cultural diversity (representing 96% of global Indigenous and non-migrant languages). Many of the NCP mapped here are left out of international agreements focused on conserving species or mitigating climate change, yet this analysis shows that explicitly prioritizing critical natural assets for NCP could simultaneously advance development, climate, and conservation goals. Crafting policy and investment strategies that protect critical natural assets is essential for sustaining human well-being and securing Earth’s life support systems.

The private sector is already experiencing the impacts of climate change, from increased operational costs to disrupted production. Investors are increasingly asking companies to disclose these risks as the physical consequences of climate change become financially material. In reviewing more than 1,600 corporate adaptation strategies, we find significant blind spots in companies’ assessments of climate change impacts and in their development of strategies for managing them. Adaptation approaches that consider broader climate change risks to supply chains, customers and employees, and that integrate ecosystem-based strategies, could limit the ‘tragedy of the horizon’ characterized by inadequate and too-late action. Investors are increasingly asking businesses to disclose their climate risk and corresponding management strategies. A review of corporate adaptation strategies reveals limited consideration of broader risks to supply chains, customers and employees.

Better land stewardship is needed to achieve the Paris Agreement's temperature goal, particularly in the tropics, where greenhouse gas emissions from the destruction of ecosystems are largest, and where the potential for additional land carbon storage is greatest. As countries enhance their nationally determined contributions (NDCs) to the Paris Agreement, confusion persists about the potential contribution of better land stewardship to meeting the Agreement's goal to hold global warming below 2°C. We assess cost-effective tropical country-level potential of natural climate solutions (NCS)—protection, improved management and restoration of ecosystems—to deliver climate mitigation linked with sustainable development goals (SDGs). We identify groups of countries with distinctive NCS portfolios, and we explore factors (governance, financial capacity) influencing the feasibility of unlocking national NCS potential. Cost-effective tropical NCS offers globally significant climate mitigation in the coming decades (6.56 Pg CO 2 e yr −1 at less than 100 US$ per Mg CO 2 e). In half of the tropical countries, cost-effective NCS could mitigate over half of national emissions. In more than a quarter of tropical countries, cost-effective NCS potential is greater than national emissions. We identify countries where, with international financing and political will, NCS can cost-effectively deliver the majority of enhanced NDCs while transforming national economies and contributing to SDGs. This article is part of the theme issue ‘Climate change and ecosystems: threats, opportunities and solutions’.

Helping the world's coastal communities adapt to climate change impacts requires evaluating the vulnerability of coastal communities and assessing adaptation options. This includes understanding the potential for 'natural' infrastructure (ecosystems and the biodiversity that underpins them) to reduce communities' vulnerability, alongside more traditional 'hard' infrastructure approaches. Here we present a spatially explicit global evaluation of the vulnerability of coastal-dwelling human populations to key climate change exposures and explore the potential for coastal ecosystems to help people adapt to climate change (ecosystem-based adaptation (EbA)). We find that mangroves and coral reefs are particularly well situated to help people cope with current weather extremes, a function that will only increase in importance as people adapt to climate change now and in coming decades. We find that around 30.9 million people living within 2km of the coast are highly vulnerable to tropical storms and sea-level rise (SLR). Mangroves and coral reefs overlap these threats to at least 5.3 and 3.4 million people, respectively, with substantial potential to dissipate storm surges and improve resilience against SLR effects. Significant co-benefits from mangroves also accrue, with 896 million metric tons of carbon stored in their soils and above- and below-ground biomass. Our framework offers a tool for prioritizing 'hotspots' of coastal EbA potential for further, national and local analyses to quantify risk reduction and, thereby, guide investment in coastal ecosystems to help people adapt to climate change. In doing so, it underscores the global role that conserving and restoring ecosystems can play in protecting human lives and livelihoods, as well as biodiversity, in the face of climate change.

In late 2020, governments will set the next decade of conservation targets under the UN Convention on Biological Diversity. Setting new targets requires understanding how well national protected area (PA) networks are spatially representing important areas for biodiversity and ecosystem services. We analyzed the representation of biodiversity priority areas (BPAs), forests, forest carbon stocks, non-timber forest products (NTFPs), and freshwater ecosystem services (FES) within terrestrial PA systems in Cambodia, Guyana, Liberia, Madagascar, and Suriname in 2003 and 2017. Four of the countries (all except Suriname) expanded their terrestrial PA networks during the study period. In all five countries, we found that PAs represented BPAs, forests, and forest carbon stocks relatively well, based on their size. PAs did not represent NTFPs and FES particularly well, except in Cambodia where FES were well represented. Countries that expanded PA networks during the study period also increased representation of forests, BPAs, and ES; in Cambodia and Madagascar these increases were substantial. Representation could be improved across all five countries, however, indicating that additional efforts are needed to safeguard biodiversity and ecosystem benefits to people in these countries.

Many human populations are dependent on marine ecosystems for a range of benefits, but we understand little about where and to what degree people rely on these ecosystem services. We created a new conceptual model to map the degree of human dependence on marine ecosystems based on the magnitude of the benefit, susceptibility of people to a loss of that benefit, and the availability of alternatives. We focused on mapping nutritional, economic, and coastal protection dependence, but our model is repeatable, scalable, applicable to other ecosystems, and designed to incorporate additional services and data. Here we show that dependence was highest for Pacific and Indian Ocean island nations and several West African countries. More than 775 million people live in areas with relatively high dependence scores. By identifying where and how people are dependent on marine ecosystems, our framework can be used to design more effective large‐scale management and policy interventions.

To stem the loss of biodiversity and ensure continued provision of essential ecosystem services world leaders adopted the 20 Aichi Biodiversity Targets in 2010, to be fulfilled by 2020. One key target (Target 11) prescribes an expansion of the global protected area system to at least 17% of land surface and 10% of oceans by 2020. Given that these targets are predominantly based on political feasibility rather than scientific evidence, it remains unclear whether fulfilment of Target 11 will suffice to safeguard biodiversity and ensure continued provision of essential ecosystem services. Despite many data gaps, in particular for ecosystem services, we can use existing global data to estimate the required protected area on land for biodiversity (a minimum of c. 17%) and biomass carbon storage (a minimum of c. 7–14% additional area to protect 75–90% of the unprotected carbon stock), which illustrates that the target of 17% of land will probably fall short in meeting these goals. As crossing thresholds or tipping points in ecosystems could trigger non-linear, abrupt change in delivery of ecosystem services, we need a science-driven understanding of how much protected, intact nature is needed to avoid unforeseen transgression of planetary boundaries.

Human activity is rapidly transforming most of Earth’s natural systems. How this transformation is impacting human health, whose health is at greatest risk, and the magnitude of the associated disease burden are relatively new subjects within the field of environmental health. We discuss what is known about the human health implications of changes in the structure and function of natural systems and propose that these changes are affecting human health in a variety of important ways.We identify several gaps and limitations in the research that has been done to date and propose a more systematic and comprehensive approach to applied research in this field. Such efforts could lead to a more robust understanding of the human health impacts of accelerating environmental change and inform decision making in the land-use planning, environmental conservation, and public health policy realms. global change | ecosystem services | ecology | planetary boundaries | ecological footprint

By promoting the conservation and restoration of natural ecosystems, policymakers have a unique opportunity to mitigate climate change while providing social and environmental benefits. Here we highlight how nature-based mitigation strategies for multiple benefits can be supported by three key areas of scientific research, drawing upon examples of research by Conservation International and its partners. First, monitoring of ecosystems can quantify the magnitude of emissions released from conversion and degradation, and can inform prioritization and planning efforts. Second, understanding the synergies and tradeoffs between climate change mitigation and other ecosystem benefits can aid in designing policy instruments, selecting management techniques and geographically targeting actions. And third, research on the design of policies, incentives and practices can enhance mitigation initiatives’ provision of both climate and noncarbon benefits. Achieving multiple benefits can in turn increase the sustainabili...

Aim Intercomparison of mechanistic and empirical models is an important step towards improving projections of potential species distribution and abundance. We aim to compare suitability and productivity estimates for a well-understood crop species to evaluate the strengths and weaknesses of mechanistic versus empirical modelling. Location South Africa. Methods We compared four habitat suitability models for dryland maize based on climate and soil predictors. Two were created using maximum entropy (MAXENT), the first based on national crop distribution points and the second based only on locations with high productivity. The third approach used a generalized additive model (GAM) trained with continuous productivity data derived from the satellite normalized difference vegetation index (NDVI). The fourth model was a mechanistic crop growth model (DSSAT) made spatially explicit. We tested model accuracy by comparing the results with observed productivity derived from MODIS NDVI and with observed suitability based on the current spatial distribution of maize crop fields. Results The GAM and DSSAT results were linearly correlated to NDVI-measured yield (R 2 = 0.75 and 0.37, respectively). MAXENT suitability values were not lin

Completely stopping fossil fuel use may not be enough to avoid dangerous climate change. Recent research on the mitigation potential of conservation, restoration, and improved land management demonstrates that natural solutions can reduce emissions and remove atmospheric CO2 while safeguarding food security and biodiversity.

Biodiversity conservation and poverty alleviation are both important societal goals demanding increasing international attention. While they may seem to be unrelated, the international policy frameworks that guide action to address them make an explicit assumption that conserving biodiversity will help to tackle global poverty. Part of the Conservation Science and Practice Series published with the Zoological Society of London, this book explores the validity of that assumption. The book addresses a number of critical questions: Which aspects of biodiversity are of value to the poor? Does the relationship between biodiversity and poverty differ according to particular ecological conditions? How do different conservation interventions vary in their poverty impacts? How do distributional and institutional issues affect the poverty impacts of interventions? How do broader issues such as climate change and the global economic system affect the biodiversity - poverty relationship at different scales? This volume will be of interest to policy-makers, practitioners and researchers concerned with understanding the potential - and limitations - of integrated approaches to biodiversity conservation and poverty alleviation.

Aim: Ecosystems face numerous well-documented threats from climate change. The well-being of people also is threatened by climate change, most prominently by reduced food security. Human adaptation to food scarcity, including shifting agricultural zones, will create new threats for natural ecosystems. We investigated how shifts in crop suitability because of climate change may overlap currently protected areas (PAs) and priority sites for PA expansion in South Africa. Predicting the locations of suitable climate conditions for crop growth will assist conservationists and decision-makers in planning for climate change. Location: South Africa. Methods: We modelled climatic suitability in 2055 for maize and wheat cultivation, two extensively planted, staple crops, and overlaid projected changes with PAs and PA expansion priorities. Results: Changes in winter climate could make an additional 2 million ha of land suitable for wheat cultivation, while changes in summer climate could expand maize suitability by up to 3.5 million ha. Conversely, 3 million ha of lands currently suitable for wheat production are predicted to become climatically unsuitable, along with 13 million ha for maize. At least 328 of 834 (39%) PAs are projected to be affected by altered wheat or maize suitability in their buffer zones. Main conclusions: Reduced crop suitability and food scarcity in subsistence areas may lead to the exploitation of PAs for food and fuel. However, if reduced crop suitability leads to agricultural abandonment, this may afford opportunities for ecological restoration. Expanded crop suitability in PA buffer zones could lead to additional isolation of PAs if portions of newly suitable land are converted to agriculture. These results suggest that altered crop suitability will be widespread throughout South Africa, including within and around lands identified as conservation priorities. Assessing how climate change will affect crop suitability near PAs is a first step towards proactively identifying potential conflicts between human adaptation and conservation planning.

Poverty and biodiversity loss are two of the world's dire challenges. Claims of conservation's contribution to poverty alleviation, however, remain controversial. Here, we assess the flows of ecosystem services provided to people by priority habitats for terrestrial conservation, considering the global distributions of biodiversity, physical factors, and socioeconomic context. We estimate the value of these habitats to the poor, both through direct benefits and through payments for ecosystem services to those stewarding natural habitats. The global potential for biodiversity conservation to support poor communities is high: The top 25% of conservation priority areas could provide 56%–57% of benefits. The aggregate benefits are valued at three times the estimated opportunity costs and exceed $1 per person per day for 331 million of the world's poorest people. Although trade-offs remain, these results show win—win synergies between conservation and poverty alleviation, indicate that effective financial mechanisms can enhance these synergies, and suggest biodiversity conservation as a fundamental component of sustainable economic development.

We evaluate the potential of a proposed policy model that would explicitly link the cultivation of biofuels with forest conservation (Biofuel þ FC ) as part of the United Nations Framework Convention on Climate Change. The model postulates that a ratio of 4:1 forest conservation to biofuel cultivation be linked to proposals for reducing emissions from deforestation and forest degradation (REDD þ Biofuel ), while a ratio of 9:1 biofuel cultivation to reforestation on degraded landscape (RDL þ Biofuel ) be linked to the afforestation/ reforestation component of the Clean Development Mechanism. Both biofuel production options would be limited to the cultivation of woody perennial biofuel species on low biomass landscapes in order to maximize the carbon benefits of the proposed policy model. The potential to conserve forest, avoid GHG emissions, improve carbon sequestration, and produce renewable energy are evaluated by an illustrative model for five case studies (Para´ e Brazil, East Kalimantan e Indonesia, Madagascar, Colombia and Liberia). The Biofuel þ FC policy model is then compared with three counterfactual scenarios: REDD Alone with no biofuel cultivation; Biofuel Alone with expanded biofuel cultivation in the absence of REDD and a Most Likely scenario where REDD and biofuel cultivation are implemented without explicit regulatory linkages. The proposed policy model would leverage forest carbon with biofuel markets, which would reduce greenhouse gas emissions and conserve biodiversity, as well as improve human welfare in developing countries, a winewinewin strategy for sustainable development.

The potential of global biodiversity conservation efforts to also deliver critical benefits, such as carbon storage and freshwater services, is still unclear. Using spatially explicit data on 3,500 range-restricted threatened species, carbon storage, and freshwater provision to people, we conducted tradeoff analyses, explicitly addressing both biodiversity and ecosystem services in selection of priority areas, to explore the potential for aligning these objectives. These analyses revealed a promising scope for aligning objectives, in particular for biodiversity and freshwater, which is not evident from previous studies that merely analyzed overlap of biodiversity and ecosystem services derived for each objective independently. However, this alignment is not complete. By revealing important synergies and tradeoffs among services, these analyzes suggest particular regions and service combinations for which spatial planning and appropriate conservation mechanisms (e.g., payments for ecosystem services) can be used to realize synergies and mitigate tradeoffs.

The extent to which an international mechanism to reduce emissions from deforestation and degradation (REDD+) can also provide biodiversity co-benefits will depend on whether the mechanism results in the retention of forest in countries harboring substantial biodiversity. Countries’ decisions whether or not to participate in REDD+ will be influenced by their national reference level of emissions from deforestation, below which their verified emissions can be credited as reductions. In this article, we explore the reduction in extinctions of forest species achieved under four alternative national reference level designs and three alternative levels of finance for REDD+. We use an 85-country partial equilibrium model and species-area relationships to estimate extinction rates for 2,472 nationally endemic forest-dependent amphibian, bird and mammal species if a REDD+ mechanism had been in place during 2005–2010. Our results indicate that elements of REDD+ that are most effective for climate change mitigation—greater finance combined with reference levels which reduce leakage by promoting broad participation across countries with both high and low historical deforestation rates—also offer the greatest benefits for biodiversity conservation.

Climate change poses profound, direct, and well-documented threats to biodiversity. A significant fraction of Earth's species is at risk of extinction due to changing precipitation and temperature regimes, rising and acidifying oceans, and other factors. There is also growing awareness of the diversity and magnitude of responses, both proactive and reactive, that people will undertake as lives and livelihoods are affected by climate change. Yet to date few studies have examined the relationship between these two powerful forces. The natural systems upon which people depend, already under direct assault from climate change, are further threatened by how we respond to climate change. Human history and recent studies suggest that our actions to cope with climate change (adaptation) or lessen its rate and magnitude (mitigation) could have impacts that match—and even exceed—the direct effects of climate change on ecosystems. If we are to successfully conserve biodiversity and maintain ecosystem services in a warming world, considerable effort is needed to predict and reduce the indirect risks created by climate change.

Species―area relationships (SARs) are a key tool for understanding patterns of species diversity. A framework for the interpretation of SARs and their prediction under different landscape configurations remains elusive, however. This article addresses one of these configurations: how species' minimum-area requirements affect the shape of island or other isolate species―area curves. We distinguish between two classes of SARs: sample-area curves, compiled entirely within larger contiguous areas, and isolate curves, compiled between isolated areas. We develop this conceptual and graphic model in order to illuminate landscape-scale diversity patterns, to discuss how various landscape and species characteristics affect outcomes, and to investigate the dynamics of local extinction under conditions of habitat fragmentation. Minimum-area effects on actual islands and other isolates predictably cause species-area curves either to be sigmoid in arithmetic space or to be lowered for smaller areas. In order to illustrate the inherent shape of isolate curves, this study fits convex and sigmoid regression models to empirical isolate (island) data sets that cover the small scales expected to include inflection points.

Well-managed protected areas (PAs) can halt habitat loss, and most countries have made commitments to expand their PA systems. Yet critics argue that even existing PAs deprive countries of needed agricultural lands and, given increased global agricultural demand, such expansion is unacceptable. This paper explores these issues at successive scales - from global to local. First, we examine potential conflicts between agriculture and PA expansion in forested regions using global-scale data. Second, we investigate the value of ecosystem services that support agriculture (e.g. erosion control, soil formation, pollination, biological control, and production of non-timber forest products) to regions identified as global priorities for biodiversity conservation, and spatially quantify the value of ecosystem services to agriculture. Third, we move to regional and national scales, examining how loss of forest services can reduce agricultural production, potentially compromising livelihoods. Finally, we ex...

Measuring the effectiveness of reserve networks is essential to ensure that conservation objectives such as species persistence are being met. We devised a new approach for measuring the effectiveness of land conservation in protecting rare and threatened species and applied it to an ecosystem of global significance. We compiled detailed global distributional data for 36 rare and threatened plants and animals found in the Lake Wales Ridge ecosystem in central Florida (U.S.A.). For each species, we developed a set of protection indices based in part on criteria used to categorize species for the World Conservation Union's Red List. We calculated protection indexes under three different conservation scenarios: a past scenario, which assumed recent, major land-acquisition efforts never occurred; a current scenario, which assumed no additional areas are saved beyond what is currently protected; and a targeted scenario, which assumed all of the remaining areas targeted for protection are eventually acquired. This approach enabled us to quantify the progress, in terms of reduced risk of extinction, that conservationists have made in protecting target species. It also revealed the limited success these land-acquisition efforts have had in reducing those extinction risks associated with loss of habitat or small geographic ranges. Many species of the Lake Wales Ridge will remain at high risk of extinction even if planned land-acquisition efforts are completely successful. By calculating protection indexes with and without each site for all imperiled species, we also quantified the contribution of each protected area to the conservation of each species, enabling local conservation decisions to be made in the context of a larger (global) perspective. The protection index approach can be adapted readily to other ecosystems with multiple rare and threatened species.

Although reserve-design algorithms have shown promise for increasing the efficiency of conservation planning, recent work casts doubt on the usefulness of some of these approaches in practice. Using three data sets that vary widely in size and complexity, we compared various decision rules for acquiring reserve networks over multiyear periods. We explored three factors that are often important in real-world conservation efforts: uncertain availability of sites for acquisition, degradation of sites, and overall budget constraints. We evaluated the relative strengths and weaknesses of existing optimal and heuristic decision rules and developed a new set of adaptive decision rules that combine the strengths of existing optimal and heuristic approaches. All three of the new adaptive rules performed better than the existing rules we tested under virtually all scenarios of site availability, site degradation, and budget constraints. Moreover, the adaptive rules required no additional data beyond what was readily available and were relatively easy to compute.

Species-area relationships (SARs) are among the most studied phenomena in ecology, and are important both to our basic understanding of biodiversity and to improving our ability to conserve it. But despite many advances to date, our knowledge of how various factors contribute to SARs is limited, searches for single causal factors are often inconclusive, and true predictive power remains elusive. We believe that progress in these areas has been impeded by 1) an emphasis on single-factor approaches and thinking of factors underlying SARs as mutually exclusive hypotheses rather than potentially interacting processes, and 2) failure to place SAR-generating factors in a scale-dependent framework. We here review mathematical, ecological, and evolutionary factors contributing to species-area relationships, synthesizing major hypotheses from the literature in a scale-dependent context. We then highlight new research directions and unanswered questions raised by this scale-dependent synthesis.

As urban areas worldwide continue to grow, the cities in which we live, work, and play can take on an increasingly vital role in sustaining biological diversity. Studies of bird communities in metropolitan areas show that our cities generally remain places inhospitable to most native bird species. However, gaps exist in our understanding of the principles needed to design metropolitan landscapes that better sustain native birds. Long-term data collected over a range of spatial scales across a city can aid in filling these gaps. To evaluate an approach to collecting such data, and to address unanswered questions concerning birds in populated areas, I organized a volunteer-based bird monitoring project (the Tucson Bird Count, or TBC) in Tucson, Arizona, USA. In the TBC, skilled observers surveyed the breeding bird community at hundreds of sites throughout Tucson. This paper reports results after the second year of this ongoing project, and has four objectives. First, it discusses issues of survey design in relation to scientific and conservation data needs. Second, it tests the ability of a citywide survey to rapidly prioritize species according to their sensitivity to development. Third, it presents a novel approach for quantifying the impact to humans of reduced diversity in urban areas. Finally, it concludes with an evaluation of the viability of volunteer-based, citywide surveys as tools for research and monitoring in cities in general, citing specific examples from this Tucson study. Volunteer-based, citywide surveys offer high visibility, efficient means to acquire data unobtainable by other methods, presenting great potential to advance ecology and conservation.

Estimating the number of species in a biogeographical province can be problematic. A number of methods have been developed to overcome sample-size limits within a single habitat. We evaluated six of these methods to see whether they could also compensate for incomplete habitat samples. We applied them to the butterfly species of the 110 ecoregions of Canada and the United States. Two of the methods use thefrequency of species that occur in afew of the sampled ecoregions. These two methods did not work. The otherfour meth- ods estimate the asymptote of the species-accumulation curve (the graph of "number of species in a set of sam- ples" versus "number of species occurrences in those samples"). The asymptote of this curve is the actual num- ber of species in the system. Three of these extrapolation estimators produced good estimates of total diversity even when limited to 10% of the ecoregions. Good estimates depend on sampling ecoregions that are hyperdis- persed in space. Clustered sampling designs ruin the usefulness of the three successful methods. To ascertain their generality, our results must be duplicated at other scales and for other taxa and in other provinces.

Acoustic communication signals change over distance due to loss of amplitude and fidelity, and it is assumed that signal degradation influences the receiver’s ability to detect and decode signals. The degree of degradation depends on the signal’s structure and the environment through which it transmits. We broadcast the advertisement calls of 22 species of Central American frogs at two heights within forested and open environments in Panama. We recorded these calls at five distances from the source and estimated signal degradation with a cross-correlation analysis, a measure that combines the effects of decrement in signal amplitude and fidelity. Calls degraded less when broadcast higher above the ground compared to on the ground, and less in open habitat compared to forested habitat; there was an additional interaction between height and environment. Furthermore, calls with low dominant frequencies experienced less degradation than calls with high dominant frequencies. There was no evidence, however, that the calls of these frogs have evolved to maximize habitat-specific transmission.

We agree with De Coster et al. (1) that researchers should assess both positive and negative impacts of changes in the structure, composition, and function of natural systems on human health. In fact, one of the key points of our report (2) is that ecosystem changes can lead to either positive or negative health consequences, or even both at the same time along different dimensions of human health. For example, the loss of a wetland may diminish water-filtration or wave-attenuation services, increasing risk of water-borne disease or flooding, yet simultaneously reduce habitat for Anopheline mosquitoes and associated risk of malaria. In other cases, positive health impacts may be experienced by one population while negative impacts are experienced disproportionately by a different group or by future generations. This mix of positive and negative impacts is why our paper emphasizes that “a particular ecosystem alteration may provide health benefits for one segment of a population while incurring health costs for another” (2). Relationships of human health to ecosystem change are complex, reinforcing the importance of considering whose health is in question, as well as the multiple dimensions of health and the possible trade-offs between both positive and negative impacts.

Global changes, from habitat loss and invasive species to anthropogenic climate change, have initiated the sixth great mass extinction event in Earth’s history. As species become threatened and vanish, so too do the broader ecosystems and myriad benefits to human well-being that depend upon biodiversity. Bringing an end to global biodiversity loss requires that limited available resources be guided to those regions that need it most. The biodiversity hotspots do this based on the conservation planning principles of irreplaceability and vulnerability. Here, we review the development of the hotspots over the past two decades and present an analysis of their biodiversity, updated to the current set of 35 regions. We then discuss past and future efforts needed to conserve them, sustaining their fundamental role both as the home of a substantial fraction of global biodiversity and as the ultimate source of many ecosystem services upon which humanity depends.

There has been a dramatic increase in the number of conservation organizations worldwide. It is now common for multiple organizations to operate in the same landscape in pursuit of different conservation goals. New objectives, such as maintenance of ecosystem services, will attract additional funding and new organizations to conservation. Systematic conservation planning helps in the design of spatially explicit management actions that optimally conserve multiple landscape features (e.g., species, ecosystems, or ecosystem services). But the methods used in its application implicitly assume that a single actor implements the optimal plan. We investigated how organizational behavior and conservation outcomes are affected by the presence of autonomous implementing organizations with different objectives. We used simulation models and game theory to explore how alternative behaviors (e.g., organizations acting independently or explicitly cooperating) affected an organization's ability to protect their feature of interest, and investigated how the distribution of features in the landscape influenced organizations' attitudes toward cooperation. Features with highly correlated spatial distributions, although typically considered an opportunity for mutually beneficial conservation planning, can lead to organizational interactions that result in lower levels of protection. These detrimental outcomes can be avoided by organizations that cooperate when acquiring land. Nevertheless, for cooperative purchases to benefit both organizations' objectives, each must forgo the protection of land parcels that they would consider to be of high conservation value. Transaction costs incurred during cooperation and the sources of conservation funding could facilitate or hinder cooperative behavior.

Alternative land uses make different contributions to the conservation of biodiversity and have different implementation and management costs. Conservation planning analyses to date have generally assumed that land is either protected or unprotected, and that the unprotected portion does not contribute to conservation goals. We develop and apply a new planning approach that explicitly accounts for the contribution of a diverse range of land uses to achieving conservation goals. Using East Kalimantan (Indonesian Borneo) as a case study, we prioritize investments in alternative conservation strategies and account for the relative contribution of land uses ranging from production forest to well-managed protected areas. We employ data on the distribution of mammals and assign species-specific conservation targets to achieve equitable protection by accounting for life history characteristics and home range sizes. The relative sensitivity of each species to forest degradation determines the contribution of each land use to achieving targets. We compare the cost effectiveness of our approach to a plan that considers only the contribution of protected areas to biodiversity conservation, and to a plan that assumes that the cost of conservation is represented by only the opportunity costs of conservation to the timber industry. Our preliminary results will require further development and substantial stakeholder engagement prior to implementation; nonetheless we reveal that, by accounting for the contribution of unprotected land, we can obtain more refined estimates of the costs of conservation. Using traditional planning approaches would overestimate the cost of achieving the conservation targets by an order of magnitude. Our approach reveals not only where to invest, but which strategies to invest in, in order to effectively and efficiently conserve biodiversity.

Natural ecosystems and biodiversity must be made a bulwark against climate change, not a casualty of it, argue Will R. Turner, Michael Oppenheimer and David S. Wilcove. This week's Nature is the third of three special issues (previously 20 November 2008 and 12 February 2009) marking the Darwin bicentenary. The theme is biodiversity and how to preserve it. Though still endangered, the golden lion tamarin is a conservation success story in an area where successes are rare: with re-introductions and efforts to preserve its Brazilian forest habitat, the population of the primate has been stabilized. The ecosystem services approach exemplified by the 1997 Nature review by Robert Costanza and colleagues, which puts a value on everything including biodiversity, is seen by many as a key to encouraging conservation: Gretchen Daily, a leading proponent, is optimistic. In an Opinion piece, Pavan Sukhdev puts the case for governmental investment in environmental services, with biodiversity properly costed as part of the broader picture. Taxonomists use part of the mitochondrial cytochrome c oxidase gene as a 'DNA bar code': more controversially, Dan Mishmar and colleagues propose that the bar code is not just a useful handle on the relatedness of species but a driver of diversity. With the Copenhagen conference looming, Will Turner, Michael Oppenheimer and David Wilcove explain how natural ecosystems and biodiversity can mitigate climate change. Robert Smith and colleagues stress the importance of local agencies — as opposed to NGOs and incomers — in setting biodiversity goals. The best biodiversity data set we have is provided by palaeontologists: Douglas Erwin thinks they could do more with it though, by adopting the techniques used by physicists. For a listing of all Darwin-related content from this issue, see the Editorial. All of this content, plus web-only material, is available at http://www.nature.com/darwin .

Priorities for conservation investment at a global scale that are based on a single taxon have been criticized because geographic richness patterns vary taxonomically. However, these concerns focused only on biodiversity patterns and did not consider the importance of socioeconomic factors, which must also be included if conservation funding is to be allocated efficiently. In this article, we create efficient global funding schedules that use information about conservation costs, predicted habitat loss rates, and the endemicity of seven different taxonomic groups. We discover that these funding allocation schedules are less sensitive to variation in taxon assessed than to variation in cost and threat. Two-thirds of funding is allocated to the same regions regardless of the taxon, compared with only one-fifth if threat and cost are not included in allocation decisions. Hence, if socioeconomic factors are considered, we can be more confident about global-scale decisions guided by single taxonomic groups.

A plot of the number of parks and other terrestrial protected areas established around the world over the past 100 years exhibits near-exponential growth, with marine parks following a similar trend. This is a testament to the growing recognition of the importance of sustaining natural systems worldwide. Yet, at the same time an expanding human population and the desire of all people for a more prosperous life have resulted in unprecedented rates of deforestation and habitat conversion. Accompanying these changes has been the spread of invasive, non-native species (including new disease organisms) to virtually all parts of the globe. With recent assessments placing 12% of the world’s birds, 23% of mammals, and 32% of amphibians in danger of extinction (Baillie et al., 2004), conservationists feel a justifiable sense of panic. Any attempt to measure the full extent of the current biodiversity crisis is made immensely more difficult by our astounding lack of knowledge about the species that share this planet with us. For example, we do not know within an order of magnitude the number of species currently present on Earth (May, 1988, 1992; Novotny et al., 2002); estimates range from 3 to more than 30 million species, of which only 1.5–1.8 million have been described to date. Not surprisingly, our inventory of the more charismatic groups of organisms, such as birds, mammals, and butterflies, is vastly more complete than our inventory of insects, arachnids, fungi, and other less conspicuous but no less important groups. If we ask the logical follow-up question—what proportion of known (described) species is in danger of extinction?—we run into a similar barrier. While organizations like the World Conservation Union (IUCN) have prepared reasonably complete assessments for a few groups, notably the charismatic vertebrates, most species are too poorly known to assess. Even within the USA only about 15% of the species catalogued to date are sufficiently known to be given any sort of conservation rank, such as endangered or not endangered (Wilcove and Master, 2005); among invertebrates that value drops to less than 5%. Compounding this shortfall of data is an equally serious shortfall of money.

The Red List Index uses information from the IUCN Red List to track trends in the projected overall extinction risk of sets of species. It has been widely recognised as an important component of the suite of indicators needed to measure progress towards the international target of significantly reducing the rate of biodiversity loss by 2010. However, further application of the RLI (to non-avian taxa in particular) has revealed some shortcomings in the original formula and approach: It performs inappropriately when a value of zero is reached; RLI values are affected by the frequency of assessments; and newly evaluated species may introduce bias. Here we propose a revision to the formula, and recommend how it should be applied in order to overcome these shortcomings. Two additional advantages of the revisions are that assessment errors are not propagated through time, and the overall level extinction risk can be determined as well as trends in this over time.

The rising prominence of more rigorous approaches to measuring conservation outcomes has included greater adoption of impact evaluation by conservation non-governmental organizations (CNGOs). Within the scientific literature, however, little consideration has been given to the unique and specific roles of CNGOs in advancing impact evaluation. We explore these issues in the context of one CNGO—Conservation International (CI)—and its experiences producing, using and funding impact evaluations over the past decade. We examine the contributions of impact evaluation to CI's mission at three different stages of CI's strategy: innovation, demonstration and amplification. Furthermore, we review incentives and barriers encountered by CI in its 10+ years' experience in impact evaluation. More coordinated and strategic use of impact evaluation by CNGOs would facilitate learning and promote accountability across the conservation community.

The measurement and analysis of biodiversity encompasses sampling strategies and statistical estimation methods for assessing the diversity of species in biological communities and provides the basis for comparison of these measurements across time and space.