Climate Change Impacts Cassava Crops
According to the Huffington Post, cassava is still a “neglected root” in most developed countries.1 I thought I had never tried the crop until I realized that its extract is tapioca. In South America the root is referred to as yucca, which is often found on menus across North America as well! The root is also called manioc, so it goes by many names as it is found in many different regions. Cassava is the third-largest source of food carbohydrates in the Tropics, after rice and maize. Around 500 million people in Africa, Asia and Latin America depend on it as a fundamental part of their diet.2 Given the importance of cassava in certain parts of the world, scientists are keeping an eye on the ways in which climate change might affect the crop given temperature and precipitation changes.
What is Cassava?
There is evidence of cassava being cultivated by the ancient Mayans in Central America dating back 1,400 years.4 Cassava cultivation soon spread to northern South America, southern Mesoamerica, and the Caribbean. In the 16th century, Portuguese traders from Brazil brought cassava to Africa, where it soon became one of the continent’s most important crops, called a “famine-reserve crop.”5 Part of the reason why cassava spread throughout the tropics is its ability to survive on marginal land. Cassava is a hardy root that survives drought better than most crops—it gives reasonable yields where many other crops do not grow well. Cassava is also a highly productive crop in terms of food calories produced per unit land area per unit of time. It can produce food calories at rates exceeding 250,000 calories/hectare/day compared with 176,000 for rice, 110,000 for wheat, and 200,000 for maize.6 The regions where cassava is grown are home to more than 30 percent of the world’s population, and their economies are almost completely dependent on agriculture.7
A Risky Business in Asia
At a recent conference in Bangkok, cassava researchers had some grim news to report. It appears that the multi-billion dollar cassava industry in South-East Asia may already be at risk due to climate change. Pramod K. Aggarwal, regional program leader for Asia at the CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS) explained: “Warmer conditions and longer dry seasons linked to climate change could prove to be the perfect catalyst for outbreaks of pests and diseases.”9 Multiple pest and disease outbreaks have occurred throughout Southeast Asia since 2009. The green mite—tiny mites that feed on leaves of cassava plants, causing them to whither and die—were first spotted in Vietnam in 2009 before they spread to Southern China and potentially could be in Cambodia by now as well. Also in 2009, Thailand faced a sudden and severe outbreak of mealybugs.10 Though the green mite and mealybug are small in size, the damage they can cause is substantial. Crop losses of around 80% are not unusual when these little bugs are involved, which is extremely detrimental to the production of subsistence farmers. These pests were rampant in Africa in the 1970s and 1980s, but were thought to be brought under control by natural enemies including a parasitoid wasp (known as E. lopezi) and a predatory mite.11 However, in Southeast Asia, these pests do not have natural enemies.
In addition to pests, climate change may also be partially responsible for extreme weather changes in Southeast Asia. Record flooding in Thailand and Southeast Asia in 2011 was preceded by a record drought in 2010. These and many other extreme weather events have impacted global food prices. As Bruce Campbell, program director at CCAFS put it, “with climate change in South and Southeast Asia expected to reduce agriculture productivity by as much as 50 percent in the next three decades, agriculture must become more productive, more resilient and more climate-friendly.”12 This entails a continued interest in breeding cassava plants with heightened pest resistance, reducing pesticide usage in an effort to avoid killing natural enemies to cassava pests, and continued introduction of predator and parasite species of pests to the cassava.13
Cassava Production in Vietnam
Hope in Africa
Despite pest problems associated with climate change problems in Southeast Asia, cassava production is actually expected to cope with climate change quite well throughout the rest of the tropics. A scientific study published in February of this year (2012), claims that cassava is “likely to outperform other crops amid rising temperatures in sub-Saharan Africa.”15 In fact, cassava may even become more productive under warming conditions.16 Scientists from the International Center for Tropic Agricultural performed the study using 24 climate and crop models, and found that cassava is expected to grow better in almost all parts of sub-Saharan Africa. The report’s lead author, climate scientist Andy Jarvis, stated:
Cassava is a survivor; it’s like the Rambo of the food crops… It deals with almost anything the climate throws at it. It thrives in high temperatures, and if drought hits it simply shuts down until the rains come again. There’s no other staple out there with this level of toughness.17
The researchers concluded that in order to reduce famine risks and improve nutrition, farmers should use cassava as a “failsafe,” but continue to plant a diversity of crops.18
Cassava’s Future
There is no way of knowing how cassava will fare in a warming climate, but there are ways to prepare for the various possibilities. Unfortunately, even though cassava can produce its starch-rich roots in poor soils and with little water, investment in cassava research has been dwarfed by work on better-known staples like rice, wheat, and maize. Further research will be essential to make cassava more resilient to pests and disease outbreaks, including such problems as green mite, whitefly, mealybug, cassava brown-streak disease and cassava mosaic disease. “Tackling cassava’s vulnerability to pests and diseases could be the final hurdle to a food secure future for millions of people,” says climate scientist Jarvis. “If we’re well prepared for these threats, cassava could be one of the most climate-change-resilient crops an African farmer can plant.”19
