Well-known examples of high-amplitude, large-scale fluctuations of small-mammal populations include vole cycles in the boreal zone of Eurasia, lemming cycles in the high-arctic tundra of Eurasia and North America, snowshoe hare cycles in the boreal zone of North America, and outbreaks of house mice in southeastern Australia. We synthesize the recent knowledge of three key aspects of these animals' population cyles: (1) periodicity, amplitude, and spatiotemporal synchrony; (2) reproduction and survival; and (3) underlying mechanisms. Survival rather than reproductive rate appears to drive rates of population increase during these fluctuations. Food limitation may stop increases of cyclic vole, lemming, and hare populations, whereas the decline from peak numbers is caused by predation mortality. In house mice, without coevolved predators, outbreaks may be driven by rainfall, food supply, and disease.

Protected-area targets of 10% of a biome, of a country, or of the planet have often been used in conservation planning. The new World Database on Protected Areas shows that terrestrial protected-area coverage now approaches 12% worldwide. Does this mean that the establishment of new protected areas can cease? This was the core question of the “Building Comprehensive Protected Area Systems” stream of the Fifth World Parks Congress in Durban, South Africa, in 2003. To answer it requires global gap analysis, the subject of the special section of BioScience for which this article serves as an introduction. We also provide an overview of the extraordinary data sets now available to allow global gap analysis and, based on these, an assessment of the degree to which existing protected-area systems represent biodiversity. Coverage varies geographically, but is less than 2% for some bioregions, and more than 12% of 11,633 bird, mammal, amphibian, and turtle species are wholly unrepresented. The global protected-area systems are far from complete.

Protected areas are the single most important conservation tool. The global protected-area network has grown substantially in recent decades, now occupying 11.5% of Earth's land surface, but such growth has not been strategically aimed at maximizing the coverage of global biodiversity. In a previous study, we demonstrated that the global network is far from complete, even for the representation of terrestrial vertebrate species. Here we present a first attempt to provide a global framework for the next step of strategically expanding the network to cover mammals, amphibians, freshwater turtles and tortoises, and globally threatened birds. We identify unprotected areas of the world that have remarkably high conservation value (irreplaceability) and are under serious threat. These areas concentrate overwhelmingly in tropical and subtropical moist forests, particularly on tropical mountains and islands. The expansion of the global protected-area network in these regions is urgently needed to prevent the loss of unique biodiversity.

Global conservation assessments require information on the distribution of biodiversity across the planet. Yet this information is often mapped at a very coarse spatial resolution relative to the scale of most land-use and management decisions. Furthermore, such mapping tends to focus selectively on better-known elements of biodiversity (e.g., vertebrates). We introduce a new approach to describing and mapping the global distribution of terrestrial biodiversity that may help to alleviate these problems. This approach focuses on estimating spatial pattern in emergent properties of biodiversity (richness and compositional turnover) rather than distributions of individual species, making it well suited to lesser-known, yet highly diverse, biological groups. We have developed a global biodiversity model linking these properties to mapped ecoregions and fine-scale environmental surfaces. The model is being calibrated progressively using extensive biological data sets for a wide variety of taxa. We also describe an analytical approach to applying our model in global conservation assessments, illustrated with a preliminary analysis of the representativeness of the world's protected-area system. Our approach is intended to complement, not compete with, assessments based on individual species of particular conservation concern.

Site conservation is among the most effective means to reduce global biodiversity loss. Therefore, it is critical to identify those sites where unique biodiversity must be conserved immediately. To this end, the concept of key biodiversity areas (KBAs) has been developed, seeking to identify and, ultimately, ensure that networks of globally important sites are safeguarded. This methodology builds up from the identification of species conservation targets (through the IUCN Red List) and nests within larger-scale conservation approaches. Sites are selected using standardized, globally applicable, threshold-based criteria, driven by the distribution and population of species that require site-level conservation. The criteria address the two key issues for setting site conservation priorities: vulnerability and irreplaceability. We also propose quantitative thresholds for the identification of KBAs meeting each criterion, based on a review of existing approaches and ecological theory to date. However, these thresholds require extensive testing, especially in aquatic systems.

Underfunding jeopardizes the ability of protected areas to safeguard biodiversity and the benefits that intact nature provides to society. In this article, we evaluate the cost of effectively managing all existing protected areas in developing countries, as well as the cost of expansion into high-priority new areas. We find that recent studies converge on a funding shortfall of $1 billion to $1.7 billion per year to manage all existing areas. The costs of establishing and managing an expanded protected-area system would total at least $4 billion per year over the next decade, an amount that far exceeds current spending but is well within the reach of the international community. These findings indicate the need for rapid action to mobilize significant new resources for the developing world's protected areas. In particular, this will require (a) the use of a range of tools to generate funds and improve efficiency of management; (b) greater precision and better communication of the costs and benefits of protected areas, both locally and globally; and (c) increased, stable support from developed countries for on-the-ground management of protected-area systems in developing countries.

Scientific imaging systems have undergone a revolution over the last century since Wilhelm Röntgen's discovery of X rays in 1895. However, deciding which imaging system will do the job and assist in solving a scientific question—not just produce beautiful graphics with little practical use—can be difficult. This article serves as a minireview of methods and applications of imaging techniques for basic research. It identifies some of the popular types of imaging systems; describes briefly how they work; and illustrates their past, present, and potential future applications. It also attempts to identify inherent pitfalls associated with some of these systems. Finally, it demonstrates some of the specific applications of scientific imaging techniques in neuroscience research.

Recent studies from my laboratory, showing the chemical castration (demasculinization) and feminization of amphibians by low but ecologically relevant concentrations of atrazine in the laboratory and in the wild, prompted a critical response from atrazine's manufacturer, Syngenta Crop Protection, and Syngenta-funded scientists. A careful analysis of the published data funded by Syngenta, and of several studies submitted to the US Environmental Protection Agency (EPA) by the Syngenta-funded panel for data evaluation, indicates that the data presented in these studies are not in disagreement with my laboratory's peer-reviewed, published data. Further, the published and unpublished data presented to the EPA by the Syngenta-funded panel (and touted in the popular press) suffer from contaminated laboratory controls; high mortality; inappropriate measurements of hormone levels in stressed, sexually immature animals during nonreproductive seasons; and contaminated reference sites. The confounding factors in the industry-funded studies severely limit any conclusions about the adverse effects of atrazine on amphibians and prevent meaningful comparisons with my laboratory's published data.