Biodiversity offsetting involves the balancing of biodiversity loss in one place (and at one time) by an equivalent biodiversity gain elsewhere (an outcome referred to as No Net Loss). The conservation science literature has chiefly addressed the extent to which biodiversity offsets can serve as a conservation tool, focusing on the technical challenges of its implementation. However, offsetting has more profound implications than this technical approach suggests. In this paper we introduce the concept of policy frames, and use it to identify four ways in which non-human nature and its conservation are reframed by offsetting. Firstly, offsetting reframes nature in terms of isolated biodiversity units that can be simply defined, measured and exchanged across time and space to achieve equivalence between ecological losses and gains. Secondly, it reframes biodiversity as lacking locational specificity, ignoring broader dimensions of place and deepening a nature–culture and nature–society divide. Thirdly, it reframes conservation as an exchange of credits implying that the value of non-human nature can be set by price. Fourthly, it ties conservation to land development and economic growth, foreshadowing and bypassing an oppositional position. We conclude that by presenting offsetting as a technical issue, the problem of biodiversity loss due to development is depoliticized. As a result the possibility of opposing and challenging environmental destruction is foreclosed, and a dystopian future of continued biodiversity loss is presented as the only alternative.

We read with great interest the opinions of Apostolopoulou & Adams (2015) on biodiversity offsetting. We agree with the authors that offsetting has more profound implications than a technical approach to the subject would suggest. Our experience with developments on the mitigation of impacts on biodiversity in government policy, financial lenders’ safeguards and corporate practice is that the political, economic, social and financial implications weigh just as heavily in decision-makers’ minds as the technical ones that Apostolopoulou & Adams raise (IFC, 2012; BBOP, 2012b; ten Kate & Crowe, 2014; IUCN, 2016; Maron et al., 2016b). The governments, companies and communities working with scientists on the mitigation hierarchy regard biodiversity offsets as one of many tools available not only for conservation but also for risk management, social and economic engagement and benefit-sharing, land-use and landscape-level planning, and sustainable development (IFC, 2012; CSBI, 2015).

Ecofeminist Maria Mies describes capitalist social relations as an iceberg. The visible tip represents the formal economy, where capitalist value emerges from exploited waged labourers and the circulation of monetized goods and assets. Underneath the waterline lurks the rest of the iceberg, and its size dwarfs the tip. Here, Mies points to a much larger world of exploitation on which commodity production and profit-making depend: women, colonies and, at the very base, nature. The bodies, places and materials of the submerged, invisible iceberg supply unwaged labour and unpriced inputs and energies that are productive; capitalism depends on this deeply undervalued work. Let us restate: capitalism exploits, yes, but strangely, it is a mode of organizing society that also relies on this exploitation. As Mies ([1986]1998, p. 200) writes, ‘the exploitation of colonies, as well as that of women and other non-wage workers, is absolutely crucial to the capitalist accumulation process’; this exploitation ‘constitutes the eternal basis for capitalist accumulation’ (Mies, 2007, p. 269).

We are grateful to ten Kate & von Hase (2016) and Dempsey & Collard (2016) for their insightful and constructive responses to our article on biodiversity offsetting (Apostolopoulou & Adams, 2015a). They agree with us that conservationists need to think very carefully about offsetting and its implications for nature conservation. They differ substantially in where that thinking should lead. Ten Kate & von Hase believe that offsetting is fine if it is done properly. Dempsey & Collard are profoundly uneasy about its implications, and go deeper into the way conservation is folded into economic development, ‘smoothing the way for new industrial scale projects’.

A project combining participatory forest management and REDD+ (Reducing Emissions from Deforestation and forest Degradation) is underway in south-eastern Tanzania. It introduces early burning practices to reduce the number and (heat) intensity of wild and late-season fires, to develop robust carbon accounting methods. Our analysis considers the causes of forest fires, and local people's knowledge of the early burning process and its impacts on livelihoods, through the development of early burning activities as a potential source of carbon revenue. Some of the difficulties of implementation have been resolved over time (e.g. the premature introduction of carbon contracts), whereas others remain: there are inequalities in knowledge, awareness and participation in early burning and the broader REDD+ process at village level. A more structured approach to early burning, with well-publicized advance planning, that includes all community members and subvillages would make a significant difference. Further challenges exist in the form of both legal and illegal hunting, a cause of forest fires that could undermine the early burning process. We argue that the long-term commitment of project managers to gain detailed knowledge of social–ecological systems, forest governance and local politics is required to successfully develop this and other similar REDD+ projects.

The objectives of No Net Loss and Net Gain have emerged as key principles in conservation policy. Both give rise to mechanisms by which certain unavoidable biodiversity losses associated with development are quantified, and compensated with comparable gains (e.g. habitat restoration). The former seeks a neutral outcome for biodiversity after losses and gains are accounted for, and the latter seeks an improved outcome. Policy-makers often assume that the transition from one to the other is straightforward and essentially a question of the amount of compensation provided. Consequently, companies increasingly favour Net Gain type commitments, and financial institutions make lending conditional on either objective, depending on the habitat involved. We contend, however, that achieving Net Gain is fundamentally different to achieving No Net Loss, and moving from one to the other is less trivial than is widely realized. Our contention is based on four arguments: (1) the two principles represent different underlying conservation philosophies; (2) ecological uncertainties make it difficult to know where the threshold between No Net Loss and Net Gain lies; (3) different frames of reference are more or less appropriate in evaluating the ecological outcomes, depending on the principle chosen; and (4) stakeholder expectations differ considerably under the two principles. In exploring these arguments we hope to support policy-makers in choosing the more appropriate of the two objectives. We suggest that financial institutions should provide greater clarity regarding the explicit requirements for each principle. We conclude by highlighting questions of relevance to this topic that would benefit from focused research.