In search of an ideal sustainable development, some alternatives are on discussion. The matter of effectiveness of environmental policies and the imperative to create mechanisms that stimulate social and economic agents to behave towards the increase on environmental protection are fundamental aspects for Law investigations.

Payment for ecosystem services has been presented as one of these alternatives. When it came to the importance for human welfare, these services, not so long ago, were neither considered by Economy nor foreseen, implicitly or explicitly, by Law.

Thus, the concept of ecosystem services and, more precisely, of biodiversity conservation, is related to the concept of positive externality, as well as pollution has been regarded as a negative externality. Therefore, recognizing the importance of ecosystem services, by means of their valuation and remuneration, means internalization of positive externalities.

Despite the potential of remuneration for such services, the idea of applying a financial-economic value to the environment alludes to the difficulty to insert new principles that go against market logics. As for Brazil, specifically, a bigger difficulty can be observed, when it comes to the need for respect towards the viewpoint that most indigenous and non-indigenous peoples have, in relation to the place where they live.

Furthermore, environmental problems present peculiarities that may not always be efficiently solved. Their action is limited by the following topics: the vastness of ecological problems and their effect on the basis of social reproduction; the social and cultural character of ecological crisis; the unprecedented and irreversible character of ecological experiments. Thus, the payment for ecosystem services implies, besides ecological aspects, debates and options strongly related to equity and social aspects.

Therefore, it is observed that these benefits will not derive automatically from payment transactions, which may evolve into a market dominated by great buyers and providers. They depend, in that manner, on the regulation that may be established, which is determining to define the agents who will have access to them and to incentive the insertion of the referred communities. These paper aims to analyze some programs of payment for ecosystem services implemented in Brazilian states, as well as Federal Law Projects and whether they seem able to fulfill equity goals.

Can it be a payment involving a certain property which was the subject of contractual exchange ? Its legitimacy is also an irritant and often subject to doctrinal differences. So, is a private person entitled to intervene, especially to identify environmental services likely to object to a fee ? Implicitly, the question of the monetary value of these services arises. What contractors is the value determined by? Unequal power relations may arise during contract negotiations. Therefore, to support opportunities for transactions to pay for environmental services, seems to compel the existence of a form of regulation. What might be the scale of action to take? By what authority? Would it necessarily be a legal regulation? Moreover, beyond "the proper functioning legal" logic of this contract, the same transposition of this legal architecture to any transaction intended to pay for environmental services also causes difficulties. Is this construction admissible to the contractors? Indeed, this generalization and / or pervasiveness of the contractual tool invites reflection on legal thought and to think of the standard.

To date, biodiversity indicators and critical habitat categories have been the subject of debate among environmental economists and conservation biologists. Legal scholarship has been largely silent on the implications of this accounting for nature. International environmental law has tended to entrench the assumptions underlying these quantitative tools, rather than to expose the ways in which quantification contributes to limited types of knowledge.

This paper seeks to map international law’s growing attempts to count nature. In so doing, it exposes the ways in which lists and numbers obscure contested knowledge. Numbers and lists are becoming the bedrock of biodiversity law. Their very appeal lies in their seeming neutrality. But who is creating the metrics? Who is doing the counting? And how does the translation of biodiversity indicators into international law and policy targets transform the information in the original indicator?

Beyond simply mapping attempts to account for nature in international law, this paper’s central concern is with the potential for greater reflexivity in international law list-making. In what ways do international environmental law’s lists and metrics allow for learning and adjustments? Given the fast-changing pace of biodiversity science, how can we better ensure that international environmental law is capable of learning and of incorporating a dynamic approach to both counting nature and understanding the limits of counting?