The labour of Nature is paid, not because she does much but because she does little. In proportion, as she becomes niggardly in her gifts, she exacts a greater price for her work. Where she is magnificently beneficent, she always works gratis." (Ricardo, 1817) conservation of nature. In addition to the conventional "efficiency" concerns that are the bread-and-butter of economists, issues like inter-generational equity also come into play.Conservation of nature might "pay" from an economic perspective: it may be rational to conserve natural capital, rather than to convert it into alternative forms of capital or to consume it today. Some forms of natural resource use leave natural habitats more or less intact -think of reduced-impact logging or sustainable fishing -while others convert natural systems into something completely different (plantation cropping, intensive farming, etc.).An overview paper that compares the profitability of various forms of land use (Balmford et al. 2001) identifies many examples where investing in nature pays: sustainable management of ecosystems yields a greater discounted flow of benefits than going for short-term gains (where discounting a flow of benefits implies carrying future benefits forward to the present, so that they are commensurate with current benefits and costs-for this purpose economists employ a discount factor). 1 To observe that nature conservation pays does not imply there are no incentives for resource managers to destroy it (or to convert it into other forms of capital). An important reason why nature may be destroyed is that many of the valuable services and benefits nature provides are "free" in the sense that they are not marketed. This is an obvious case of market failure. Even if nature is valuable, as long as it does not command a flow of money, its value tends to be ignored by private parties. Examples include the air purifying qualities of ecosystems, but also non-use values associated with biodiversity conservation.Environmental economists have developed methods to attach monetary values to ecosystem services, but that is not the same as money-in-the-bank. The point is that even if the social 1 Of course counter-examples also exist; sometimes converting natural capital to financial capital provides higher returns. This is particularly probable when natural resource stocks are plentiful, and when the perspective of private investors or resource owners is adopted (see below).