Reforesting the Amazon

Why Agricultural Intensification Is Key to Restoring the World's Tropical Forests

Conservation International recently launched the world’s biggest tropical reforestation project in the Amazon. The scale of it is huge: 73 million trees covering 70,000 hectares of degraded land. Only China and Africa’s Great Green Wall projects are more ambitious.

The scheme is clearly good news. But even as we celebrate restorative efforts like this one, we need to remain focused on the root causes of deforestation. Protecting primary forests requires concrete steps to address the greatest threat of all: agriculture.

In the Amazon, as in most tropical forest regions, agricultural expansion, whether for cropland or pasture, is the single biggest driver of deforestation.1,2,3 Much of the debate about how to limit agriculture’s impact on nature has focused on whether land sharing or land sparing approaches are more effective. The former is concerned with increasing biodiversity on farmland. However, this is likely to come at the cost of yields for many systems, resulting in greater expansion. The latter proposes that yields be maximized on existing land to reduce expansion. However, this is likely to come at the cost of biodiversity on the farm.

One of the big questions this debate raises is around the trade-offs for biodiversity between agricultural expansion and intensification. This is the question at the heart of a recent paper led by Laura Kehoe, whose findings send a clear message. Reducing agricultural expansion is the single greatest priority for minimizing biodiversity loss in the largest remaining tracts of tropical forest in the world—the Amazon and Congo basins. Further, and perhaps not surprisingly, expansion was also more likely to lead to overlap with priority conservation areas, such as IUCN protected areas, and regions with the smallest human footprint—the so-called “last of the wild.”4

That is not to say that intensification does not come at a cost. In regions of the world where the human footprint is already high, and where little scope exists for expansion, such as India and Eastern Europe, the risks of intensification were deemed severe. Nor is the reality of the debate so clear-cut. There are multiple cultural, ecological, and economic drivers of land use that may favor numerous landscape configurations.

But the research highlights a crucial point. For the world’s most biodiverse and intact tropical forests, avoiding expansion of agricultural lands must be a priority for conservation.

The good news is that many of the regions of the world that would benefit most from agricultural intensification are also those where the greatest scope for improvement exists. Whether rice in Indonesia, maize in Brazil, or beef and dairy in Africa,5 there are countless examples where significant improvements could be made. It has been estimated that potential maize yields in Brazil, for example, are on average 86% higher than what is actually achieved.6 In 2013, the average beef cattle in Africa produced 40% less meat per animal than cattle in Europe.7 Closing these yield gaps may help reduce expansion of cropland and pasture in some of the earth’s most biodiverse systems.

Nor do these changes necessarily require radical changes to local production systems. A recent review of livestock production systems in six sub-Saharan African countries demonstrated that milk yields could be improved by as much as 167% and chicken production by 127% simply by adopting local best practice.

Closing these yield gaps is about more than just reducing deforestation and sparing land for nature. Raising yields has a direct correlation to reducing poverty in smallholder agriculture8 and was considered a foundation for the social and economic change heralded by the industrial revolutions in Britain and China.9,10 Recent research by John McArthur and Gordon McCord found that each half ton increase in yields led to a 14–19% increase in per-capita GDP.

Perhaps most compelling are Bronson Griscom’s recent findings that show that avoided deforestation has the second greatest carbon mitigation potential after, yes, reforestation. Indeed, even the reforestation potential hinges in large part on improving agricultural efficiency. In Griscom’s analysis, 42% of the modeled reforestation mitigation depended on a reduced need for pasture brought about by dietary shifts and more efficient beef production.

Of course, intensification creates its own problems that will need to be dealt with carefully. Higher yields can lead to rebound, increasing the opportunity costs of leaving potentially productive land fallow. In Tanzania, Arild Angelsen and colleagues showed that higher yields and and greater profitability were correlated with agricultural expansion, while similar trends were found in cocoa plantations in West Africa.11

Higher land rents associated with more profitable agriculture also increase the costs of conservation. This was demonstrated in simulations by Jacob Phelps and colleagues that showed that higher maize and cassava yields increased the cost of REDD+ schemes in the Democratic Republic of Congo owing to higher agricultural land rents.

Thus, any developments that seek to spare land via intensification must be accompanied by appropriate policy measures to prevent rebound and ensure that conservation co-benefits are realized.12 This will require, among much else, effective land zoning policies, appropriate economic incentives, transparent and accountable supply chains, and an integrated approach to landscape planning.

And that brings us back to Conservation International’s Amazon reforestation project. As encouraging as the project is, care must be taken to ensure that it avoids the issues faced by China’s Great Green Wall, where scientists have questioned whether reforestation is simply displacing deforestation elsewhere, and in more biodiverse and delicate habitats. If the laudable ambition of the project is to be realized, it will be essential that further expansion elsewhere is curtailed. And for that to happen, we need to get serious about how best to intensify agricultural production in an ecologically and socially sustainable way.

1. Osvaldo E. Sala, F. Stuart Chapin, III, Juan J. Armesto, Eric Berlow, Janine Bloomfield, Rodolfo Dirzo, Elisabeth Huber-Sanwald, Laura F. Huenneke, Robert B. Jackson, Ann Kinzig, Rik Leemans, David M. Lodge, Harold A. Mooney, Martı́n Oesterheld, N. LeRoy Poff, Martin T. Sykes, Brian H. Walker, Marilyn Walker, Diana H. Wall, “Global Biodiversity Scenarios for the Year 2100,” Science 287, no. 5459 (2000): 1770–1774,

2. Elizabeth Barona, Navin Ramankutty, Glenn Hyman, and Oliver T. Coomes, “The role of pasture and soybean in deforestation of the Brazilian Amazon,” Environmental Research Letters 5, no. 2 (2010).

3. Matthew G. Betts, Christopher Wolf, William J. Ripple, Ben Phalan, Kimberley A. Millers, Adam Duarte, Stuart H. M. Butchart, and Taal Levi, “Global forest loss disproportionately erodes biodiversity in intact landscapes,” Nature 547 (2017): 441–444, https://doi:10.1038/nature23285.

4. Eric W. Sanderson, Malanding Jaiteh, Marc A. Levy, Kent H. Redford, Antoinette V. Wannebo, and Gillian Woolmer, “The Human Footprint and the Last of the Wild: The human footprint is a global map of human influence on the land surface, which suggests that human beings are stewards of nature, whether we like it or not,” BioScience 52, no. 10 (2002): 891–904,[0891:THFATL]2.0.CO;2.

5. FAOSTAT, Food and Agriculture Organization of the United Nations (2017).

6. Data from For Brazil, simulated average weighted maize yield, Yw = 8.69 t/ha. Actual reported maize yield = 4.67 t/ha. Yield gap = (8.69-4.67)/4.67 = 0.86.

7. Data from FAOSTAT. Average cattle yield in Africa = 155 kg/animal.

8. Pablo Tittonell and Ken E. Gillerb, “When yield gaps are poverty traps: The paradigm of ecological intensification in African smallholder agriculture,” Field Crops Research 143 (2013): 76–90,

9. P. K. O’Brien, “Agriculture and the Industrial Revolution,” The Economic History Review 30 (1977),

10. Jikun Huang and Scott Rozelle, “Agricultural development and policy before and after China’s WTO accession,” in Agriculture and Food Security in China: What Effect WTO Accession and Regional Trade Agreements?, ed. Chunlai Chen and Ron Duncan (ANU Press, 2008), 27–54.

11. Robert M. Ewers, Jörn P. W. Scharlemann, Andrew Balmford, and Rhys E. Green, “Do increases in agricultural yield spare land for nature?” Global Change Biology 15, no. 7 (2009): 1716–1726,

12. Ben Phalan, Rhys E. Green, Lynn V. Dicks, Graziela Dotta, Claire Feniuk, Anthony Lamb, Bernardo B. N. Strassburg, David R. Williams, Erasmus K. H. J. zu Ermgassen, and Andrew Balmford, “How can higher-yield farming help to spare nature?” Science 351, no. 6272: 450–451,