human population growth, and increased per-capita impact of people.

climate in many parts of the world tends to vary not just from year to year but also on a multi-decade time scale;

Montana’s environmental problems today include almost all of the dozen types of problems that have undermined pre-industrial societies in the past, or that now threaten societies elsewhere in the world as well. Particularly conspicuous in Montana are problems of toxic wastes, forests, soils, water (and sometimes air), climate change, biodiversity

The other camp holds that environmentalists’ concerns are exaggerated and unwarranted, and that continued economic and population growth is both possible and desirable.

the complexity of ecosystems often makes the consequences of some human-caused perturbation virtually impossible to

The processes through which past societies have undermined themselves by damaging their environments fall into eight categories, whose relative importance differs from case to case: deforestation and habitat destruction, soil problems (erosion, salinization, and soil fertility losses), water management problems, overhunting, overfishing, effects of

Globalization makes it impossible for modern societies to collapse in isolation,

A third consideration is hostile neighbors.

For 81 Pacific islands my colleague Barry Rolett and I graded the extent of deforestation on a numerical scale, and we also graded values of nine input variables (such as rainfall, isolation, and restoration of soil fertility) postulated to influence deforestation. By a statistical analysis we were able to calculate the relative strengths with