Richard B. Norgaard
Modern economics started out strongly rooted in the natural sciences. During the eighteenth century, a group of French economists called themselves "physiocrats" because they aspired to build economics up from physical principles. In their early input-output models, the primary productivity of nature combined with agricultural labor limited activity at the secondary and tertiary levels of industry and commerce. Thomas Malthus argued that disease and war stemmed from human population exceeding nature's carrying capacity. In the early nineteenth century, David Ricardo explained the distribution of income between landlords and laborers through a model based on differences between the natural productivity of the best lands and those of lower quality.
Early economic thinking enriched subsequent biological thought. The physiocrats' reasoning parallels models of how primary producers limit throughput in food chains. Both Charles Darwin and Alfred Russell Wallace credited Malthus for identifying how environmental limits can lead to natural selection. Ricardo's model of increasing agricultural production underlies the ongoing discussion in conservation biology with respect to whether intensifying production through the use of chemicals on the best lands is better for biodiversity than extending production to marginal lands. Explanations of optimal foraging behavior and predator-prey interactions also have parallels in early economic models.
Early economic thinkers were heavily influenced by the success of physics and tried to imitate its cause-and-effect reasoning. Physics envy continues to this day, but somewhere along the way, economics lost its roots to physical reality As the industrial revolution evolved into an agricultural revolution as well, farm output no longer seemed to be tied to natural conditions. The idea that the whole economy was limited by nature fell out of fashion among economists in the beginning of the twentieth century. Ecological reasoning, which was still in its infancy at the time, did not help people-perhaps especially economists-to see how industrialization had merely shifted agriculture's dependence on nature in space and time. While the productivity of individual farms became less and less dependent on the qualities of particular soils, on the timing of pest outbreaks, and on the weather patterns of specific years, farms collectively became more and more dependent on the watersheds that provided the irrigation water, on the rapid evolution of insects in response to synthetic pesticides, and on the ability of downstream ecosystems to process organic and chemical wastes. Economic reasoning became formalized and institutionalized in public decision-making before biologists and the public became ecologically aware. Indeed, significant scientific awareness of the interrelationships between agriculture, biodiversity, and climate change has arisen only during the past quarter-century. For this reason, there is now great interest in connecting ecological and economic thinking again.
Can we integrate ecological models of natural systems undisturbed by humans with economic models of human activity that do not include nature? Should we? Can we measure the value of an ecological service based on other prices observed in real markets that do not value ecosystem services sufficiently in the first place? And should we? Can we extend models of ecological systems to include human activity when people's choices are driven by changing tastes and needs? Ecological understanding is rooted in multiple patterns of reasoning: energetics, food webs, evolutionary ecology, and so on. Similarly, economists understand economic systems through multiple patterns of thinking. Individual models from ecology and economics might integrate, but how do we bring the full wisdom of the members of the two fields together to form something wiser still? The articles in this issue raise all of these questions and more. Our future hinges on ecologists and economists working on the answers together.