Local ecological knowledge has been subject to a great deal of debate in recent decades. Early strands of this literature could be easily classified into two camps - one which purports the adaptive logic and scientific validity of local knowledge, and the other which seeks to expose its flaws by illustrating its divergence from scientific understandings. While acknowledging subsequent attempts to question this dichotomy (Agrawal (Development and Change 26:413-439, 1995); Long (Development Sociology: Actor Perspectives. London and New York: Routledge, 2001); Pottier et al. (Negotiating Local Knowledge: Power and Identity in Development. London: Pluto Press, 2003)), this chapter maintains the distinction as a means of exploring claims to validity of diverse bodies of knowledge. It does this through a series of case studies on biophysical processes that have been subject to much debate and misunderstanding in both public and scientific spheres. Local and scientific knowledge are juxtaposed in two ways. By highlighting biophysical processes for which local and scientific understandings diverge but for which local ecological knowledge is nevertheless functionally sound, the adaptive capacity of local knowledge is illustrated. As is shown, empirical foundations to local ecological knoweldge may be found even behind purportedly "erroneous" perceptions of cause and effect. Secondly, by exposing the subjectivities of scientific understandings on certain biophysical processes, the grounding of even the most "objective" knowledge in perceptual and political biases is illustrated. Case studies on shifting agriculture, watershed function, and ecological processes that challenge our predictive capacities help to illustrate both the scientific foundations of local knowledge and the "perceptual" foundations of science. The intention is neither to discredit scientific understandings nor to place undue emphasis on the merits of local ways of knowing, but rather to expose the unfair value judgements leveraged against the latter historically - and to call for a more even playing field in the politics of environmental knowledge.