Contrary to the general trend in the tropics, forests have recovered in Puerto Rico from less than 10% of the landscape in the late 1940s to more than 40% in the present. The recent Puerto Rican history of forest recovery provides the opportunity to study the ecological consequences of economic globalization, reflected in a shift from agriculture to manufacturing and in human migration from rural to urban areas. Forest structure rapidly recovers through secondary succession, reaching mature forest levels of local biodiversity and biomass in approximately 40 years. Despite the rapid structural recovery, the legacy of pre-abandonment land use, including widespread abundance of exotic species and broadscale floristic homogenization, is likely to persist for centuries.

Our central paradigm for urban ecology is that cities are emergent phenomena of local-scale, dynamic interactions among socioeconomic and biophysical forces. These complex interactions give rise to a distinctive ecology and to distinctive ecological forcing functions. Separately, both the natural and the social sciences have adopted complex system theory to study emergent phenomena, but attempts to integrate the natural and social sciences to understand human-dominated systems remain reductionist—these disciplines generally study humans and ecological processes as separate phenomena. Here we argue that if the natural and social sciences remain within their separate domains, they cannot explain how human-dominated ecosystems emerge from interactions between humans and ecological processes. We propose an integrated framework to test formal hypotheses about how human-dominated ecosystems evolve from those interactions.

The Multiscale Experimental Ecosystem Research Center has conducted a series of mesocosm experiments to quantify the effects of scale—in terms of time, depth, radius, exchange rate, and ecological complexity—on biogeochemical processes and trophic dynamics in a variety of coastal habitats. The results indicate that scale effects can be categorized as (a) fundamental effects, which are evident in both natural and experimental ecosystems, and (b) artifacts of enclosure, which are solely attributable to the artificial environment in mesocosms. We conclude that multiscale experiments increase researchers' understanding of scale in nature and improve their ability to design scale-sensitive experiments, the results of which can be systematically compared with each other and extrapolated to nature.

Current assessments of climate-change effects on ecosystems use two key approaches: (1) empirical synthesis and modeling of species range shifts and life-cycle processes that coincide with recent evidence of climate warming, from which scenarios of ecosystem change are inferred; and (2) experiments examining plant–soil interactions under simulated climate warming. Both kinds of assessment offer indisputable evidence that climate change and its effects on ecosystems are ongoing. However, both approaches often provide conservative estimates of the effects of climate change on ecosystems, because they do not consider the interplay and feedback among higher trophic levels in ecosystems, which may have a large effect on plant species composition and on ecosystem services such as productivity. Understanding the impacts of these top-down processes on ecosystems is critical for determining large-scale ecosystem response to climate change. Using examples of links between climate forcing, trophic interactions, and changes in ecosystem state in selected terrestrial, freshwater, and marine systems, we show that the ability to understand and accurately forecast future effects of climate change requires an integrated perspective, linking climate and the biotic components of the ecosystem as a whole.

Neither biologists nor nonbiologists in today's society are paying adequate attention to the escalating ethical issues raised by the human predicament, and the expertise of biologists seems to demand they make additional contributions to environmental ethics, broadly defined. Massive environmental destruction and the development of biological and nuclear weapons have changed the world; cultural evolution of ethics has not kept pace. “Bioethics” must be expanded from its focus on medical issues to consider such things as the ethics of preserving natural capital for future generations and those of dealing with overconsumption. Bioethics should examine issues as diverse as the ethics of invading Iraq to increase the role of the rich in generating climate change and the ethics of the Lomborg affair. Achieving a sustainable global society will require developing an agreed-upon ethical basis for the necessary political discourse, and the time to start is now.

The US Forest Service has proposed new regulations under the National Forest Management Act that would replace a long-standing requirement that the agency manage its lands “to maintain viable populations of existing native and desired non-native vertebrate species.” In its place, the Forest Service would be obligated merely to assess ecosystem and species diversity. A landscape assessment process would rely on ecosystem-level surrogate measures, such as maps of vegetation communities and soils, to estimate species diversity. Reliance on such “coarse-filter” assessment techniques is problematic because there tends to be poor concordance between species distributions predicted by vegetation models and observations from species surveys. The proposed changes would increase the likelihood of continued declines in biodiversity and fail to address the original intent of the act. We contend that responsible stewardship requires a comprehensive strategy that includes not only coarse-filter, ecosystem-level assessment but also fine-filter, species-level assessments and viability assessments for at-risk species.

Science faculty who want to improve instructional strategies need to design appropriate methods for assessing and analyzing classroom data to determine the effectiveness of their approaches to learning. We used systematic strategies derived from methods of discipline-based science research to design problems to assess students' understanding of the carbon cycle in two introductory biology courses for science majors. Among typical misconceptions are the ideas that gaseous carbon dioxide is not respired during decomposition by organisms in the soil and that plants acquire carbon from the soil rather than from the air through leaves during photosynthesis. Diagnostic problems provided data on students' understanding and misconceptions. In-class instruction, problems, and laboratories were designed to focus on student misconceptions and provided formative assessment. After two semesters, results indicated that the majority of students responded accurately; however, 20 to 40 percent of the students maintained misconceptions even after instruction. Assessment strategies enabled us to collect, analyze, and report data that will influence future instruction.