The combined forces of El NinoSouthern Oscillation (ENSO) eventsand global warming are likely to have dramatic effects on future cropproduction and food security in Indonesia and other tropical countries.Indonesia consistently experiences dry climatic conditions and droughtsduring El Nino events, resulting in delayed production of rice—thecountry’s primary food staple—and exacerbated problems of foodinsecurity among the poor. Our preliminary analysis suggests thatglobal climate change could cause Indonesia’s “normal” climate state tobe similar to an El Nino state currently. Unfortunately, globalclimate models (GCMs) link poorly to regional hydrologic conditions in thetropics, and have limited coverage of the Indonesian archipelago, excludingareas representing 75% of the population and 66% of the riceproduction (Figure 1). Therefore results from the GCM need to befurther “downscaled” to understand the effects of global climate changeon Indonesian hydrology and agriculture.

Land use has generally been considered a local environmental issue, but it is becoming a
force of global importance. Worldwide changes to forests, farmlands, waterways, and
air are being driven by the need to provide food, fiber, water, and shelter to more than
six billion people. Global croplands, pastures, plantations, and urban areas have expanded
in recent decades, accompanied by large increases in energy, water, and fertilizer consumption, along with considerable losses of biodiversity. Such changes in land use have
enabled humans to appropriate an increasing share of the planet's resources, but they
also potentially undermine the capacity of ecosystems to sustain food production,
maintain freshwater and forest resources, regulate climate and air quality, and ameliorate
infectious diseases. We face the challenge of managing trade-offs between immediate
human needs and maintaining the capacity of the biosphere to provide goods and
services in the long term.

Global society is seriously threatened by the environmental impacts of human activities. Although the Millennium Ecosystem Assessment and the Intergovernmental Panel on Climate Change have been established to analyze biophysical aspects of global change, there is no equivalent effort to assess the role of individual behavior in creating those environmental threats. The authors of this Policy Forum propose the institution of a Millennium Assessment of Human Behavior to establish serious dialogues about what can and should be done. It would draw heavily on social scientists and would engage groups of citizens globally in public forums to explore the moral elements and the consequences of choices about environmental change.

Biological productivity in most of the world's oceans is controlled by the supply of nutrients to surface waters. The relative balance between supply and removal of nutrients-including nitrogen, iron and phosphorus-determines which nutrient limits phytoplankton growth. Although nitrogen limits productivity in much of the ocean, large portions of the tropics and subtropics are defined by extreme nitrogen depletion. In these regions, microbial denitrification removes biologically available forms of nitrogen from the water column, producing substantial deficits relative to other nutrients. Here we demonstrate that nitrogen-deficient areas of the tropical and subtropical oceans are acutely vulnerable to nitrogen pollution. Despite naturally high nutrient concentrations and productivity, nitrogen-rich agricultural runoff fuels large (54-577 km2) phytoplankton blooms in the Gulf of California. Runoff exerts a strong and consistent influence on biological processes, in 80% of cases stimulating blooms within days of fertilization and irrigation of agricultural fields. We project that by the year 2050, 27-59% of all nitrogen fertilizer will be applied in developing regions located upstream of nitrogen-deficient marine ecosystems. Our findings highlight the present and future vulnerability of these ecosystems to agricultural runoff.

The depletion of many marine fisheries has created a new impetus to expand seafood production through fish farming, or aquaculture. Marine aquaculture, especially of salmon and shrimp, has grown considerably in the past two decades, and aquaculturists are also beginning to farm other marine species. Production data for salmon and shrimp indicate that farming supplements, rather than substitutes for fishing. Since most farmed marine fish are carnivores, farming them relies on the capture of finite supplies of wild fish for use in fish feeds. As aquaculture is not substituting for wild fisheries, heavy dependence on wild fish inputs is a concern as marine aquaculture grows. Other likely impacts include escapes of farmed fish and large-scale waste discharges from fish farms. A viable future for marine ecosystems will require incorporation of ecological perspectives into polices that integrate fishing, aquaculture, and conservation.