Many demographers criticized this definition as being too broad, though the criticisms implied less of a problem with the concept itself than a difficulty in isolating the environmental dimension from the social and economic conditions with which causal factors are interlinked. In 1994, Astri Surkhe argued that environmental "push" factors could not be considered outside the wider context of the socioeconomic development process. He observed, "In a broader development perspective, environmental degradation appears as a proximate cause of migration, while the underlying factors are population pressures and patterns of resource use" (Surkhe, 1994). In response to Hurricane Katrina, anthropologist Anthony Oliver- Smith noted that the "increasing complexity of [natural] disasters is rooted in the interplay of social and economic factors in the environment, exacerbating the vulnerability of people- and environments and intensifying impacts when they occur." (Oliver-Smith, 2005).
Other attempts at operationalizing environmentally induced refugee movements have refined the definition further, distinguishing "voluntary" or "proactive" migrants, who may have left their place of origin due to environmental factors but generally made a conscious choice to do so, from "forced," "reactive" migration where people had little or no choice but to be displaced. Surkhe noted that "common forms of environmental degradation may cause both deliberate migration and acute displacement" (Surkhe, 1994). Some, like British demographer Anthony Richmond, conceptualized a continuum between "proactive migrants seeking to maximize net advantage, and the reactive behavior of those whose degrees of freedom are severely constrained" (Richmond,1993).
A working definition of "environmental refugees" for this paper will focus on those for whom the environmental "push factors" for migration are dominant, operating "with respect to the most common forms of environmental degradation, including deforestation, rising sea levels, desertification and drought.
