In their policy forum ("The limits of consensus," 14 September 2007, P. 1505), M. Oppenheimer et al, make several misleading statements. They suggest that a premature drive for consensus led Working Group I to understate the risk of large future sea-level rise in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (WGI-AR4). (Letters)

A common assumption is that ecosystem services respond linearly to changes in habitat size. This assumption leads frequently to an "all or none" choice of either preserving coastal habitats or converting them to human use. However, the researchers survey of wave attenuation data from field studies of mangroves, salt marshes, seagrass beds, nearshore coral reefs, and sand dunes reveals that these relationships are rarely linear.

Wetland management may be improved by evaluating nonlinear relationships of economic value and ecological services.

As a result of recent infrastructure failures the U.S. Senate passed the National Infrastructure Improvement Act (NIIA), which would create the National Commission on the Infrastructure and its ability to meet current and future demands. Such policy development coincides with ongoing efforts to manage and restore degraded ecosystems.

In the News Focus Story, "Greening the Meeting" (5 October 2007, P. 36), B. Lester compares the fossil fuel energy required to transport scientists to and from a conference by airplane to the energy used by "2250 Honda Civics during a year's worth of normal driving." Another way to put a human face on fossil energy usage is to think in terms of "Virtual Persons" (VPs). (Letters)

The Turonian (93.5 to 89.3 million years ago) was one of the warmest periods of the Phanerozoic eon. It has been argued that there may have been several stages of continental ice growth during the period, reflected in both erosional surfaces and geochemical records associated with possible glaciation-induced sea-level falls.

The forest biome of Amazonia is one of Earth's greatest biological treasures and a major component of the Earth system. This century, it faces the dual threats of deforestation and stress from climate change. In this article, the authors summarize some of the latest findings and thinking on these threats, explore the consequences for the forest ecosystem and its human residents, and outline options for the future of Amazonia.

The consequences of global climate change are profound, and the scientific community has an obligation to assess the ramifications of policy options for reducing greenhouse gas emissions and enhancing CO2 sinks in reservoirs other than the atmosphere. Ocean iron fertilization (OIF), one of several ocean methods proposed for mitigating rising atmospheric CO2, involves stimulating net phytoplankton growth by releasing iron to certain parts of the surface ocean.

A major attempt to streamline-or, critics claim, politicize-the revision of important air-quality standards has run into trouble. One year ago, the U.S. Environmental Protection Agency (EPA) overhauled its lengthy process of updating the National Ambient Air Quality Standards (NAAQS), which have far-reaching impacts on many regulations. Some critics feared the move would allow politics to trump science by giving agency appointees more say and sidelining external scientific review.

In a research by paleoceanographer Andre Bornemann of Leipzig University in Germany and his colleagues analyzed apparently unaltered Foraminifera picked from sediment core drilled from Demerara Rise beneath the western equatorial Atlantic. Following a classic technique, the researchers measured oxygen isotopes in the forams' shells. They found a sharp shift toward the heavier oxygen-18 isotope in both surface and bottom dwelling forams from 91.2 million years ago.