Low yields, in turn, cause more forest land to be cleared in an attempt to satisfy food demands. Related research makes use of a rich panel data set on national income and investment, across countries over time, allowing more detailed study of the political factors that matter for investment. This work focuses on the role of complementarity and substitution between natural resource stocks and manmade capital. Such relationships can create feedbacks between two, which can either augment or diminish the direct effect of ownership on natural resource use. An example of complementarity is the relationship between roads and forests.
Roads are capital, and they are generally cited as an important proximate cause of deforestation.
Societies that are relatively unstable may fail to investment in roads, and might therefore experience relatively slow deforestation. An example of substitution is the one mentioned earlier. Stability may lead to more extensive investments in agricultural capital, which may retard the clearing of forests. This idea has been examined empirically for both forests and petroleum resources. One significant empirical finding from this research is that petroleum exploration and production rates are strongly associated with ownership risk.