Zero net deforestation is the wrong target, warn experts

Environmental initiatives that target zero net deforestation may miss their mark when it comes to slowing climate change and protecting biodiversity, warns a commentary published in this week’s issue of the journal Science.

While zero net deforestation may seem like a worthy target in efforts to curb forest loss, Sandra Brown and Daniel Zarin argue that the goal is at best, ambiguous, and at worst, may lead to perverse outcomes for the world’s forests.

“As global interest in reducing deforestation has grown, numerous governments, corporate groups, and civil society organizations have set time-bound targets for achieving ‘zero deforestation.’ Some targets specify ‘net deforestation,’ some ‘gross deforestation,’ and some do not specify at all,” the authors write. “Public- and private-sector policy-makers who commit to deforestation reduction targets, and those who advocate for them, are often unclear about their implications. This lack of clarity may lead to perverse outcomes, including governments celebrating reductions of deforestation when large areas of native forest have been cut down and ‘zero deforestation’ certification of agricultural commodities produced on land recently cleared of native forest cover.”

Conversion to plantations in Borneo

Conversion to plantations in Borneo

To maximize the environmental benefits of maintaining forest cover, Brown and Zarin argue for setting two targets: reducing clearing of native forests, which store more carbon and house more wildlife than plantations and regrowing forests, and reforesting already-cleared lands.

“Net deforestation targets, inherently and erroneously, equate the value of protecting native forests with that of planting new ones,” they write, noting that “zero net deforestation does not mean zero net carbon emissions.”

To illustrate the point, Brown and Zarin lay out a scenario where 100,000 hectares of native forest per year is converted, while an equivalent area if replanted or restored.

For example, a zero net deforestation commitment may include conversion of 100,000 ha per year of native forest, with high carbon stocks, to agricultural commodity production and the reforestation of an equivalent area with secondary forest regrowth or new plantations that remove smaller quantities of carbon. If we assume that native forest biomass has an average carbon stock of 150 metric tons of carbon per hectare and the reforested area sequesters carbon at an annual rate of 5 tons of carbon per year the net annual emissions would be 14.5 million metric tons of carbon per year. Achieving zero net emissions in this example would require that for every 1 ha deforested, 30 ha would have to be reforested.

Thus a singular focus on zero net emissions could potentially result in both greater emissions and increased biodiversity loss. As such, Brown and Zarin recommend targeting reducing gross deforestation.

“If the intent is to reduce carbon emissions, conserve biodiversity, and protect hydrological services, then reducing gross deforestation will generally have a better outcome than reducing net deforestation,” they write.

The idea of focusing on reducing native forest loss is not new, in fact it is already embodied in the most recent framework for the U.N.’s Reducing Emissions from Deforestation and Degradation (REDD+) program, which “[prohibits] counting any carbon accumulation in plantations that substitute for native forests within countries’ voluntary commitments to REDD+,” according to the authors.

Several voluntary initiatives, including the World Wildlife Fund’s (WWF) 2020 goal of zero net deforestation, also explicitly exclude plantations.

By some definitions, like the one used by the U.N. Food and Agriculture, this isn't deforestation

By some definitions, like the one used by the U.N. Food and Agriculture, this isn’t deforestation

A more targeted focus will be made easier by recent advancements in forest monitoring, including today’s release of a Google-powered interactive global forest map that shows both forest loss and forest gain since 2000. The developments will make it easier to separate tree plantations from native forests and understand the history of each pixel on a satellite image, allowing analysts to distinguish between old-growth forest and regrowing forest.

But shifting the goalposts won’t be embraced by all. The logging and plantation industries in particular have often opposed efforts to exclude natural forest conversion and first-time logging of primary forests from compensation under carbon offset programs. However if policymakers are serious about reducing emissions from deforestation and preserving biodiversity, Brown and Zarin argue that the days of generalizing need to come to an end.

“As an idea, zero deforestation is compelling. It seems simple and precise, and therefore attractive. But as a global target, it means much more than what is achievable if the meaning is ‘gross,’ and much less if it is ‘net.’ Intentionally or not, these terms are being used ambiguously and sometimes interchangeably, which fosters confusion and sets the stage for perverse outcomes,” they write. “Governments, corporations, and nongovernmental organizations should instead set separate, ambitious targets for reductions in gross deforestation and for reforestation. Some gross deforestation targets, including for commodity production in transition countries, could be actionable at or near zero; others could not. Until targets are clarified, and metrics agreed upon, zero may mean nothing at all.”

Forest loss by country graph


Sandra Brown and Daniel Zarin. What Does Zero Deforestation Mean? SCIENCE VOL 342 15 NOVEMBER 2013
Matt Hansen et al. High-Resolution Global Maps of 21st-Century Forest Cover Change. SCIENCE VOL 342 15 NOVEMBER 2013

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