Core MAN015 from Pacific coastal Guatemala contains sediments accumulated in a mangrove setting over the past 6500 yr. Chemical, pollen, and phytolith data, which indicate conditions of estuarine deposition and terrigenous inputs from adjacent dry land, document Holocene climate variability that parallels the Maya lowlands and other New World tropical locations. Human population history in this region may be driven partly by climate variation: sedentary human populations spread rapidly through the estuarine zone of the lower coast during a dry and variable 4th millennium B.P. Population growth and cultural florescence during a long, relatively moist period (2800–1200 B.P.) ended around 1200 B.P., a drying event that coincided with the Classic Maya collapse.

Sustainable development requires that population and consumption remain within the limits of carrying capacity, while preventing a decline in the carrying capacity of an area requires that productive systems implanted through development be sustainable. Zoning can be a valuable tool in influencing land-use decisions, but we cannot expect government decrees to be capable of causing the landscape to evolve toward the sustainable patterns which have been recommended through zoning. A prerequisite for influencing land-use change is understanding the social processes involved in land-use decisions, beginning with deforestation dynamics. Work to estimate carrying capacity needs to embrace the wide variety of production systems used and contemplated for Amazonia and to be able to interpret this information at scales ranging from local communities to the region as a whole. This will require not only studies of different land-use systems in rural areas, but also integration with studies of energy use and support limits of urban populations. Risks of environmental impacts must be quantified under different development scenarios, and limits of acceptable risk identified and integrated into analyses of carrying capacity.

Tapping the value of environmental services of standing forest represents a promising means of sustaining Amazonia's population over the long term, but numerous obstacles exist. These include halting deforestation before opportunities are lost and supporting the population in non-damaging ways while the institutional groundwork is laid for using the environmental services involved. Research is needed to quantify the magnitude of services and the appropriate monetary value per unit of service. Diplomatic agreement must be reached on these values, which can be expected to be quite different from estimates of the 'true' values based on research. A series of social arrangements must be proposed and implemented if the value derived from environmental services is to fulfil its dual role of maintaining both the forest and the human population in Amazonia.