Human impacts on the natural environment have reached such proportions that in addition to an Ôextinction crisisÕ, we now also face a broader Ôbiome crisisÕ. Here we identify the world's terrestrial biomes and, at a finer spatial scale, ecoregions in which biodiversity and ecological function are at greatest risk because of extensive habitat conversion and limited habitat protection. Habitat conversion exceeds habitat protection by a ratio of 8 : 1 in temperate grasslands and Mediterranean biomes, and 10 : 1 in more than 140 ecoregions. These regions include some of the most biologically distinctive, species rich ecosystems on Earth, as well as the last home of many threatened and endangered species. Confronting the biome crisis requires a concerted and comprehensive response aimed at protecting not only species, but the variety of landscapes, ecological interactions, and evolutionary pressures that sustain biodiversity, generate ecosystem services, and evolve new species in the future.

U.S. land management can contribute 1.2 Pg CO2e year−1 of greenhouse gas mitigation, 76% of which costs USD 50 Mg CO2e−1 or less.

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Protected areas (PAs) are a cornerstone of conservation efforts and now cover nearly 13% of the world's land surface, with the world's governments committed to expand this to 17%. However, as biodiversity continues to decline, the effectiveness of PAs in reducing the extinction risk of species remains largely untested. We analyzed PA coverage and trends in species' extinction risk at globally significant sites for conserving birds (10,993 Important Bird Areas, IBAs) and highly threatened vertebrates and conifers (588 Alliance for Zero Extinction sites, AZEs) (referred to collectively hereafter as ‘important sites’). Species occurring in important sites with greater PA coverage experienced smaller increases in extinction risk over recent decades: the increase was half as large for bird species with>50% of the IBAs at which they occur completely covered by PAs, and a third lower for birds, mammals and amphibians restricted to protected AZEs (compared with unprotected or partially protected sites). Globally, half of the important sites for biodiversity conservation remain unprotected (49% of IBAs, 51% of AZEs). While PA coverage of important sites has increased over time, the proportion of PA area covering important sites, as opposed to less important land, has declined (by 0.45–1.14% annually since 1950 for IBAs and 0.79–1.49% annually for AZEs). Thus, while appropriately located PAs may slow the rate at which species are driven towards extinction, recent PA network expansion has under-represented important sites. We conclude that better targeted expansion of PA networks would help to improve biodiversity trends.

The potential for conservation of individual species has been greatly advanced by the International Union for Conservation of Nature's (IUCN) development of objective, repeatable, and transparent criteria for assessing extinction risk that explicitly separate risk assessment from priority setting. At the IV World Conservation Congress in 2008, the process began to develop and implement comparable global standards for ecosystems. A working group established by the IUCN has begun formulating a system of quantitative categories and criteria, analogous to those used for species, for assigning levels of threat to ecosystems at local, regional, and global levels. A final system will require definitions of ecosystems; quantification of ecosystem status; identification of the stages of degradation and loss of ecosystems; proxy measures of risk (criteria); classification thresholds for these criteria; and standardized methods for performing assessments. The system will need to reflect the degree and rate of change in an ecosystem's extent, composition, structure, and function, and have its conceptual roots in ecological theory and empirical research. On the basis of these requirements and the hypothesis that ecosystem risk is a function of the risk of its component species, we propose a set of four criteria: recent declines in distribution or ecological function, historical total loss in distribution or ecological function, small distribution combined with decline, or very small distribution. Most work has focused on terrestrial ecosystems, but comparable thresholds and criteria for freshwater and marine ecosystems are also needed. These are the first steps in an international consultation process that will lead to a unified proposal to be presented at the next World Conservation Congress in 2012.Establecimiento de Criterios para la Lista Roja de UICN de Ecosistemas AmenazadosResumenEl potencial para la conservación de muchas especies ha avanzado enormemente porque la Unión Internacional para la Conservación de la Naturaleza (UICN) ha desarrollado criterios objetivos, repetibles y transparentes para evaluar el riesgo de extinción que explícitamente separa la evaluación de riesgo de la definición de prioridades. En el IV Congreso Mundial de Conservación en 2008, el proceso comenzó a desarrollar e implementar estándares globales comparables para ecosistemas. Un grupo de trabajo establecido por la UICN ha formulado un sistema inicial de categorías y criterios cuantitativos, análogos a los utilizados para especies, para asignar niveles de amenaza a ecosistemas a niveles local, regional y global. Un sistema final requerirá de definiciones de ecosistemas; cuantificación del estatus de ecosistemas; identificación de las etapas de degradación y pérdida de los ecosistemas; medidas de riesgo (criterios) alternativas; umbrales de clasificación para esos criterios y métodos estandarizados para la realización de evaluaciones. El sistema deberá reflejar el nivel y tasa de cambio en la extensión, composición, estructura y funcio...