Classical morphological studies of plant development have provided a sound basis for recent advances in molecular and computational tools for understanding how leaves become leaves. Research on mutants in model organisms has identified networks of genes that are involved in the development of leaves. Mutant analyses and gene expression studies have also revealed epigenetic phenomena that regulate leaf development. Such techniques are still invaluable to developmental biology, and these techniques are continuing to be enhanced. Each new technique or species studied appears to reveal further levels of complexity in the regulation of leaf development. Only by drawing together evidence from numerous techniques and comparative studies of a wide array of species will we understand how such diversity of plant form has arisen. In this article we do not provide a comprehensive review of our current understanding of leaf development, but rather a glimpse at how advances in technologies facilitated that understanding.

This overview examines the status and trends of seafood production, and the positive and negative impacts of aquaculture on biodiversity conservation. Capture fisheries have been stabilized at about 90 million metric tons since the late 1980s, whereas aquaculture increased from 12 million metric tons in 1985 to 45 million metric tons by 2004. Aquaculture includes species at any trophic level that are grown for domestic consumption or export. Aquaculture has some positive impacts on biodiversity; for example, cultured seafood can reduce pressure on overexploited wild stocks, stocked organisms may enhance depleted stocks, aquaculture often boosts natural production and species diversity, and employment in aquaculture may replace more destructive resource uses. On the negative side, species that escape from aquaculture can become invasive in areas where they are nonnative, effluents from aquaculture can cause eutrophication, ecologically sensitive land may be converted for aquaculture use, aquaculture species may consume increasingly scarce fish meal, and aquaculture species may transmit diseases to wild fish. Most likely, aquaculture will continue to grow at significant rates through 2025, and will remain the most rapidly increasing food production system.

Wetlands perform many essential ecosystem services—carbon storage, flood control, maintenance of biodiversity, fish production, and aquifer recharge, among others—services that have increasingly important global consequences. Like biodiversity hotspots and frontier forests, the world's largest wetlands are now mapped and described by an international team of scientists, highlighting their conservation importance at the global scale. We explore current understanding of some ecosystem services wetlands provide. We selected four of these wetlands (the largest peatland, West Siberian Lowland; the largest floodplain, Amazon River Basin; the least-known wetland, Congo River Basin; and the most heavily developed wetland, Mississippi River Basin), and we illustrate their diversity, emphasizing values and lessons for thinking big in terms of conservation goals. Recognizing the global significance of these wetlands is an important first step toward forging global conservation solutions. Each of the world's largest wetlands requires a basinwide sustainable management strategy built on new institutional frameworks—at international, national, and regional levels—to ensure provision of their vital services.

The Okavango Delta, Botswana, is a major wetland surrounded by the Kalahari Desert. The delta supports a diverse fish fauna that depends on highly seasonal flooding from inflowing rivers, and on the actions of ecosystem engineers (hippopotamuses, elephants, and termites), for creation and maintenance of their habitats. Conflicts in resource use, especially water, are likely to affect fish populations and the Okavango ecosystem in the near future. We present conceptual models of this remarkable aquatic ecosystem in relation to fish and fisheries as the basis for future research and conservation efforts. Developing understanding of the environmental flow requirements of the delta is key to the management of the Okavango Delta as an ecosystem supporting diverse and abundant fish and wildlife. Once developed, this understanding can be used to allocate water within the Okavango watershed.

Disputes over conflicting information from different studies play a prominent role in many environmental controversies. Rather than resulting from flawed or fraudulent science, we suggest that conflicting findings may often result from the complex nature of environmental systems and the limitations of our analytical tools. Using heuristic simulation examples, we show how environmental heterogeneity and limitations in our ability to measure and model environmental systems can give rise to conflicting inferences even for very simple systems. Although analytical tools are improving, individual studies will remain limited in their ability to describe complex environmental systems. We suggest that, instead of being a curse, multiple studies with conflicting findings often provide an opportunity to expand and refine our understanding of complex environmental systems. Using hierarchical Bayesian techniques, we show how pooling multiple studies can enable us to generate a broader, richer, and more accurate understanding of the dynamics of a system and to better estimate our uncertainties.

Biodiversity offsets provide a mechanism for maintaining or enhancing environmental values in situations where development is sought despite detrimental environmental impacts. They seek to ensure that unavoidable negative environmental impacts of development are balanced by environmental gains, with the overall aim of achieving a net neutral or positive outcome. Once the decision has been made to offset, multiple issues arise regarding how to do so in practice. A key concern is site selection. In light of the general aim to locate offsets close to the affected sites to ensure that benefits accrue in the same area, what is the appropriate spatial scale for identifying potential offset sites (e.g., local, ecoregional)? We use the Marxan site-selection algorithm to address conceptual and methodological challenges associated with identifying a set of potential offset sites and determining an appropriate spatial scale for them. To demonstrate this process, we examined the design of offsets for impacts from development on the Jonah natural gas field in Wyoming.