Population, Resources, and David Harvey
Harvey's thesis is that political ideologies determine choice of research methodologies, which in turn predetermine the outcome of the research -- outcomes which then give seemingly impartial justification for the original political ideology. So Malthus (a defender of the landed classes) and Ricardo (an apologist for capitalism) were led to choose, respectively, the hypothetico-deductive and abstract modeling approaches, which led them to conclude that population would inevitably outstrip resources and plunge the masses into poverty. On the other hand, the socialist Marx was able to use the methodology of dialectics to see that population pressure on resources is not a universal, but rather is created by the way capitalism shapes people's wants. Modern neo-Malthusian environmentalists (such as the authors of The Limits to Growth) use updated versions of the hypothetico-deductive and abstract modeling methodologies, so it's no surprise that they come to Malthusian conclusions. Unfortunately, despite environmentalists' sincerity of concern, such conclusions are useful for the capitalist system -- and so should be abandoned in favor of Marx's dialectical analysis (as was done, he says, in China under Mao).
Harvey shows that each of the three men have the stated combination of political ideology, research methodology, and conclusions. But he does little to show that there is a necessary relation between them -- that a hypothetico-deductive approach will inevitably conclude that population is outstripping resources, for example. And in fact the history of the Limits to Growth debate show quite clearly that Harvey's thesis is wrong -- because it has no place for cornucopians like Julian Simon. Cornucopians make good use of Ricardo-style abstract economic models to show that the free market will stave off a population crisis, and bring prosperity to everyone, through new technologies and resource substitution. They also look to hypothetico-deductive procedures for support, most famously in Simon's (successful) bet with Limits-to-Growth-er Paul Ehrlich over the prices of various minerals. Indeed, the interesting thing here is that Ricardo and Simon could come to such diametrically opposed conclusions about population, resources, and the welfare of the masses, yet each see their conclusions as justifications for capitalism. The ability to get the political conclusions you want transcends any dependence on research methodology.
So what is Harvey's (and Marx's) big conclusion as to why the Limits to Growth thesis is wrong? He says that population pressure on resources could be solved not only by reducing population, but also by changing the per capita consumption level, or developing new technologies and social systems that expand our resource base and allow us to use it more efficiently. This is quite true -- but it's hardly a radical reframing of the issue. And we didn't need a Marxist to point it out. "Consume less" is the standard environmentalist line (indeed, today Malthusian scenarios are usually invoked to prove the need for lower consumption rather than lower birthrates). And "find new technologies" is the standard moderate and anti-environmentalist line. Either dialectical thinking is unnecessary for reaching Harvey's conclusions, or dialectics is far more commonplace than any of the radical academics extolling its subversive virtues would be willing to admit.
I think that this is symptomatic of a lot of "radical" research. Conclusions that are really fairly straightforward are dressed up in language implying the need for a radical philosophical change in order to be able to see the issue. But if even I can understand -- and agree with -- your conclusions, then they don't depend on "dialetics" or a "relational ontology."