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Dietary diversity: key to defending tropical ecosystems

A new study published in the Proceedings of the National Academy of Sciences (PNAS) points to the homogenization of global diets over the past fifty years. It shows that worldwide production of traditional staples such as millet, rye, sorghum, yams and cassava have been in decline. Instead, the world’s population increasingly relies on a relatively small number of “megacrops” like wheat, corn and soy, raising serious concerns for global food security, human nutrition, and the genetic diversity of crops.

In terms of their growing contribution of calories to global diets since the 1960s, two crops that stand out are soybeans and palm
oil. The sudden rise of soy and palm oil underlines just how central dietary changes have been in driving tropical deforestation.

Brazil is the world’s second largest producer and exporter of soybeans, and the crop has become an increasingly central threat to
biodiversity and forest cover in the southern Amazon. Much of the demand for soybeans is related to its role as feed for livestock,
another major threat to forests in Brazil and elsewhere.

Across the world in Indonesia and Malaysia, oil palm plantations have replaced tropical forests on a massive scale since the 1990s. This has increased greenhouse gas emissions and destroyed the habitats of orangutan and many other endangered species. Severe haze in Southeast Asia linked to expanding palm oil production has impacted human health and made international headlines.

Local and international efforts have succeeded in raising awareness of these problems. Environmentally-conscious consumers are increasingly wary of consuming soy and palm oil products. A long and growing list of companies have therefore made commitments to using certified sustainable palm and soy products, while plantation companies are pledging not to contribute to deforestation. Improving environmental practices in soybean and palm oil production is welcome and should continue.

However, the long-term trend in global diets, rising human populations, and climate change show that such efforts may not be enough. As long as the consumption of globally-sourced vegetable oils and animal products continues to climb, the economic pressure on
tropical forests will increase as a result. Diversified, locally-oriented food systems are ultimately the only sustainable

CITATION: Colin K. Khourya,b,1, Anne D. Bjorkmanc,d, Hannes Dempewolfd,e,f, Julian Ramirez-Villegasa,g,h, Luigi Guarinof, Andy Jarvisa,g, Loren H. Riesebergd,e,i, and Paul C. Struikb. Increasing homogeneity in global food supplies and the implications for food security. PNAS, 2014 DOI: 10.1073/pnas.1313490111

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