Ecological research of microorganisms sensu latu (archaea, bacteria, protists, viruses) has come of age within the last few decades. This newfound importance is a consequence of a greater appreciation for the enormous diversity present among these unseen entities, and an increasing recognition of the pivotal roles that these species play in food-web processes and geochemical cycles in aquatic and terrestrial ecosystems. These advances are due in large part to the incorporation of modern genetic and immunological approaches into ecological and physiological studies of natural assemblages and pure cultures of microorganisms. Molecular approaches have revolutionized bacterial and archaeal biology, and are beginning to transform our understanding of protistan ecology (unicellular eukaryotic algae and protozoa). Recent efforts have greatly improved our comprehension of the evolutionary relationships among protistan taxa; documented the existence of lineages of previously undetected protists; and catalyzed studies characterizing their diversity, nutritional modes, and trophic interactions. These extraordinary findings are only beginning to unfold as genetic databases for protists expand and as ecologists learn to interpret and exploit this wealth of genetic information.

Biological field stations are distributed throughout North America, capturing much of the ecological variability present at the continental scale and encompassing many unique habitats. In addition to their role in supporting research and education, field stations offer legacies of data, specimens, and accumulated knowledge. Such legacies often provide the only framework for documenting and understanding the nature and pace of ecosystem, regional, and global changes in environmental conditions; ecological processes; and biodiversity. Because of these legacies and because they serve as gathering places for a rich diversity of highly creative and motivated scientists, students, and citizens, biological field stations are frequently where serendipitous scientific discoveries take place. The inclusion of biological field stations in environmental observatories and research networks ensures that these places will continue to foster future serendipitous scientific discoveries.

Recent declines in amphibian diversity and abundance have contributed significantly to the global loss of biodiversity. The fungal disease chytridiomycosis is widely considered to be a primary cause of these declines, yet the critical question of why amphibian species differ in susceptibility remains unanswered. Considerable evidence links environmental conditions and interspecific variability of the innate immune system to differential infection responses, but other sources of individual, population, or species-typical variation may also be important. In this article we review the preliminary evidence supporting a role for acquired immune defenses against chytridiomycosis, and advocate for targeted investigation of genes controlling acquired responses, as well as those that functionally bridge the innate and acquired immune systems. Immunogenetic data promise to answer key questions about chytridiomycosis susceptibility and host-pathogen coevolution, and will draw much needed attention to the importance of considering evolutionary processes in amphibian conservation management and practice.

In an energy-scarce future, ecosystem services will become more important in supporting the human economy. The primary role of ecology will be the sustainable management of ecosystems. Energy scarcity will affect ecology in a number of ways. Ecology will become more expensive, which will be justified by its help in solving societal problems, especially in maintaining ecosystem services. Applied research on highly productive ecosystems, including agroecosystems, will dominate ecology. Ecology may become less collegial and more competitive. Biodiversity preservation will be closely tied to preservation of productive ecosystems and provision of high ecosystem services. Restoration and management of rich natural ecosystems will be as important as protection of existing wild areas. Energy-intensive micromanagement of ecosystems will become less feasible. Ecotechnology and, more specifically, ecological engineering and self-design are appropriate bases for sustainable ecosystem management. We use the Mississippi River basin as a case study for ecology in times of scarcity.

The Precambrian world, biologically speaking, was remarkably simple and populated exclusively by microbes. In sharp contrast, our contemporary biological world is perceived as remarkably diverse and complex. What were the processes that facilitated the emergence of biological complexity from simplicity during the course of Earth's history? They would certainly include (a) the major transitions in evolution, such as the emergence of oxygenic photosynthesis and aerobic respiration, supported by a benign geochemistry that enabled evolutionary processes; (b) the leap in biological complexity from prokaryotes to unicellular and then multicellular eukaryotes, which led to phagotrophy and the evolution of food chains; and (c) establishment of an elevated and stable atmospheric oxygen tension that molded a biosphere capable of supporting large, complex organisms and their evolutionary radiations. Here, we attempt to analyze the fundamental reality of biological complexity by tracing the path from microbes in Earth's early anoxic atmosphere to the biological complexity of the contemporary aerobic biosphere, which is apparently more complex than life in the early Precambrian.

A new hypothesis suggests that forest cover plays a much greater role in determining rainfall than previously recognized. It explains how forested regions generate large-scale flows in atmospheric water vapor. Under this hypothesis, high rainfall occurs in continental interiors such as the Amazon and Congo river basins only because of near-continuous forest cover from interior to coast. The underlying mechanism emphasizes the role of evaporation and condensation in generating atmospheric pressure differences, and accounts for several phenomena neglected by existing models. It suggests that even localized forest loss can sometimes flip a wet continent to arid conditions. If it survives scrutiny, this hypothesis will transform how we view forest loss, climate change, hydrology, and environmental services. It offers new lines of investigation in macroecology and landscape ecology, hydrology, forest restoration, and paleoclimates. It also provides a compelling new motivation for forest conservation.