When Piers Blaikie wrote The Political Economy of Soil Erosion in Developing Countries in 1985, he helped lay the groundwork for what eventually would come to be known as 'political ecology' (so argue Raymond Bryant and Michael K. Goodman, 2008). Before then, explain Bryant and Goodman, the assumption in geography and other disciplines was that the environment could be understood and managed through natural science models. But with Blaikie's 1985 book, political economy became a defining factor in interpreting environmental change and degradation. At this point, political economy was already a well established term, but political ecology was not. Thus, in part, the latter can arguably be seen as a play-on term stemming from the former.
In English, the term 'political economy' dates back to Sir James Steuart’s An Inquiry into the Principles of Political Oeconomy (1776). Following Steuart, political economy became a well-established field of inquiry, practiced most famously throughout the Eighteenth and Nineteenth Centuries by Adam Smith, David Hume, Jean-Baptiste Say, David Ricardo, John Stuart Mill, Thomas Malthus, and of course, the field's biggest critic - Karl Marx. For the most part, these authors saw themselves as 'political economists' - hence the title of Marx's formative Outlines of the Critique of Political Economy (1858).
Yet the foundational authors of political ecology may not necessarily have interpreted their project in those terms. As Blaikie has explained (2007), most of the authors who, like himself, were associated with political ecology (PE), were associated ex post: "By the end of the 1980s PE as a self-conscious reference point began to appear and authors such as Blaikie and Brookfield (1987), Bassett (1988), Black (1990), Bryant (1992), Neumann (1992), Moore (1993), Escobar (1996), Muldavin (1996), Bryant and Bailey (1997), Scott and Sullivan (2000) amongst many others, began to use the term and thereby proclaimed themselves as operating in and thus defining, the field" (Blaikie, 2007: 766). In the 1990s key texts (by Zimmerer and Basset, 2003; Peet and Watts, 2004; and Robbins, 2004) helped to further add definition to this 'field'.
Nevertheless, the term 'political ecology' originally dates back to the 1935, when it was oddly used as a heading for a column by Frank Thone in The Science News Letter discussing the role of grass as a cause of war. Then again the term was used (in somewhat of a different context) by Albert Lepawsky (1936) in an article in The American Political Science Review about political reforms then being carried by the German Reich ("State boundaries and state sovereignty can be liquidated, but can the Nazis transform the political ecology of a country which... is the most urban in the world...?")!
Throughout the ensuing decades the term 'political ecology' is used in a variety of contexts, but it is not until the 1970s that it begins to take on something akin to its contemporary meaning of "an approach to... the complex metabolism between nature and society" (Eric Sheppard, The Dictionary of Human Geography, 2009). Outside of the academy, the term was used to refer to the politicization of environmental problems - in short, it came to be associated with the environmental movement itself! In the academy, political ecology seems to arise from a confluence of three subfields: cultural ecology, ecological anthropology, and Marxist-inspired political economy. These influences finally come together in Piers Blaikie's seminal book, and the rest is history.