Review
Agricultural expansion and its impacts on tropical nature

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Highlights

  • Agriculture will increase dramatically in tropical nations this century.

  • This expansion will have major impacts on tropical forests and semi-arid environments.

  • The rapid proliferation of roads will strongly influence the footprint of agriculture.

  • Changes will be most dramatic in South America and Sub-Saharan Africa.

The human population is projected to reach 11 billion this century, with the greatest increases in tropical developing nations. This growth, in concert with rising per-capita consumption, will require large increases in food and biofuel production. How will these megatrends affect tropical terrestrial and aquatic ecosystems and biodiversity? We foresee (i) major expansion and intensification of tropical agriculture, especially in Sub-Saharan Africa and South America; (ii) continuing rapid loss and alteration of tropical old-growth forests, woodlands, and semi-arid environments; (iii) a pivotal role for new roadways in determining the spatial extent of agriculture; and (iv) intensified conflicts between food production and nature conservation. Key priorities are to improve technologies and policies that promote more ecologically efficient food production while optimizing the allocation of lands to conservation and agriculture.

Section snippets

A tropical time bomb

Tropical ecosystems sustain much of Earth's biological diversity [1], provide myriad natural products and services to local communities [2], and play key roles in the global carbon and hydrological cycles 3, 4. Unfortunately, many tropical ecosystems are being disrupted by large-scale land-use change and other environmental alterations [5]. Such changes are an important source of greenhouse gas emissions 3, 6 and are likely to have serious, if uncertain, impacts on biodiversity 5, 7, 8, 9.

Expanding agriculture

The global footprint of agriculture is likely to increase markedly this century–indeed, the global extent of cropland is currently expanding faster than at any time in the past 50 years [23]. A study that extrapolated into the future based on linear trends from the early 1960s to 2000, when global food production doubled, concluded that ∼1 billion ha of additional land, mostly in developing nations, would need to be converted to agriculture by 2050 to meet projected demands [10]. This is a land

Impacts of agricultural change on tropical nature

Because they are so far-reaching, the environmental changes detailed above will have a wide array of impacts on tropical ecosystems and biota. Here we highlight some of the most important potential changes.

Key challenges ahead

Over the course of the 21st century, humanity will face unprecedented environmental and societal challenges, many of which will play out in the tropics. Here we highlight some urgent priorities and opportunities for confronting these challenges.

First, food needs to be produced where people live, and that means increasing production in the tropics, where the greatest population growth is occurring. The good news is that there are large yield gaps in the tropics and thus considerable potential to

Concluding remarks

Human societies are remarkably adaptable but, as the 21st century progresses, we are moving ever farther into uncharted territory. Tropical ecosystems are crucial for global biodiversity and provide vital ecosystem services, but are facing unprecedented pressures. The already-massive global footprint of agriculture is expanding rapidly, especially in Sub-Saharan Africa and South America. Its impacts on terrestrial and aquatic ecosystems will be intense and increasingly pervasive.

Pressing

Acknowledgments

We thank Andrew Balmford, David Edwards, Ivette Perfecto, Ben Phalan, Thomas Rudel, Sean Sloan, John Vandermeer, and two anonymous referees for many useful insights.

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