如今，尼亚基向卢索托区（Lushoto）的其他农民传授他的经验。一些邻居正在尝试在他那里见效的农耕做法。尼亚基是世界各地数百万正在采用更有效也更环保的可持续农耕方式的农民之一。可持续农业提倡的方法在经济上可行，有益环保，并且有利于保护公众健康。

可持续发展之路

农民和商业食品行业都为满足世界需要取得了显著进步。二十五年前，世界上营养不良的人口占23％。如今，联合国（United Nations）公布的数字已下降到13％。

但这一成就是有代价的：森林砍伐和动植物栖息地丧失、珍贵的水资源枯竭、农田水土流失及其对海洋和土壤的污染，以及其他土壤问题。在过去50年里，农业、林业和渔业所排放的温室气体几乎翻了一倍。

我们面临的挑战： 2050年的世界人口预计将达到90亿，如何在养活这么多人的同时保护环境和气候？这意味着要在使用更少的土地和资源的情况下，生产出比目前多70％的粮食作物。

一个国际专家小组说，在全球范围内坚持实行可持续农业能够帮助农民战胜这一挑战。吉姆·霍恩（Jim Horne）在Freshgreens网说：“可持续性是一种必需，而不是奢谈。”霍恩是位于俄克拉何马州波托（Poteau，Oklahoma）的克尔可持续农业中心（Kerr Center for Sustainable Agriculture）的负责人，合著有《下一场绿色革命：健康和可持续农业的基本步骤》（The Next Green Revolution: Essential Steps to a Healthy, Sustainable Agriculture）一书。

事半功倍

斯坦福大学（Stanford University）的帕梅拉·马特森（Pamela Matson）对learner.org说：“我看到转向可持续发展的大潮。关键是，我们的行动必须更迅速。”一些国家的政府、科学家和非政府组织正在帮助农民实现这种转变。

轮作和滴灌的用水较少，也很少用或根本不用化学肥料。免耕种植——这是一种不耕垦从而不破环土壤的种植农作物或牧草的方式——可以提高20％的玉米产量。这一种植方式与可持续灌溉的做法相结合有可能使产量增长近70％。

美国农民采用的一些新型农业技术在2015年米兰世博会（Milan Expo）的美国馆（U.S. Pavillion）展出。

以农民为本

可持续农业能让农民受益。提高产量和降低化肥和农药开支意味着收入提高，并且减少接触有害化学物质。

但是，农民有时会害怕改变，也会缺乏资金和足够的信息，并且不信任陌生人的指点。农业合作社和农民田间学校——这些是交流想法和知识的网络——有助于促进采取可持续方法。政府可以为农民改变做法提供帮助。

当越南官方推广水稻强化栽培方法（System of Rice Intensification，SRI）时，取得了减少用肥用水而多打粮的效果。

像美国的“保障未来粮食供给”（Feed the Future）这样的国际项目致力于开发有针对性的气候智能型的技术和方法。而且农工商业和食品公司也能有所作为。如金宝汤公司（Campbell Soup Company）和通用磨坊（General Mills）这样的企业都在供应链采用了可持续的做法。在印度，可口可乐公司（Coca-Cola）和当地的非政府组织培训安得拉邦（Andhra Pradesh）种植芒果的农民，并为他们提供设施，推广滴灌和其他可持续发展的方法。

变革的种子

开展科研是将来取得更大进步的关键。“项目催化剂”（Project Catalyst）项目推动农民进行创新，以减少农药和化肥流入澳大利亚的大堡礁（Great Barrier Reef）泻湖。在农民几乎买不起化肥的撒哈拉以南非洲地区（sub-Saharan Africa），很多农民现在采用“微剂量”法，也就是精确按照每个种坑的需要量施肥。他们的高科技工具：一个瓶盖。

在未来十年里，研究人员希望培育出用肥少但产量高的作物品种。

康奈尔大学（Cornell University）的诺曼·厄普霍夫（Norman Uphoff）说，最大的希望在于人们要更好地理解数十亿微生物在植物和土壤的肥力中发挥的作用。他说， “我们需要一场哥白尼式的革命来利用这些微生物的潜力。”

With billions to feed, sustainable agriculture is not a luxury
 

Peter Nyaki has learned a thing or two about soil erosion. The soil on his tree and vegetable farm in Tanzania was losing nutrients and becoming less and less fertile, while his harvests were meager — until he tried a new approach, using organic manure and sowing grasses to prevent runoff during the rainy season. Now his small farm supports a variety of healthy crops, including beans whose harvests have increased more than 60 percent.

Nyaki is sharing what he has learned with fellow farmers in the Lushoto district. Some of his neighbors are trying out agricultural practices proven on his land. Nyaki is one of millions of farmers around the world who are making agriculture both more efficient and environmentally friendly by adopting sustainable practices. Sustainable agriculture promotes methods that are economically viable, environmentally sound and protect public health.

The path to sustainability

Farmers and the commercial food industry have made significant progress in feeding the world. Twenty-five years ago, 23 percent of the world’s population was undernourished. Today, says the United Nations, the figure is down to 13 percent.

But this achievement has come at a price: deforestation and habitat loss; depletion of scarce water resources; pollution of land and sea from farm runoff; soil erosion; and other soil problems. And greenhouse gas emissions from agriculture, forestry and fisheries have nearly doubled over the past 50 years.

The challenge: how to feed the 9 billion people expected in 2050 while preserving the environment and climate. In other words, produce 70 percent more food using less land and fewer resources.

Sustainable agriculture practiced consistently on a global scale can help farmers meet that challenge, says a team of international experts. “Sustainability is a necessity, not a luxury,” Jim Horne told the Freshgreens website. Horne heads the Kerr Center for Sustainable Agriculture in Poteau, Oklahoma, and co-authored The Next Green Revolution: Essential Steps to a Healthy, Sustainable Agriculture.

Harvesting more with less

“I see great movement toward a transition to sustainability,” Stanford University’s Pamela Matson told learner.org. “The key is that we’re going to have to move a lot faster.” Some governments, scientists and NGOs are helping farmers make this transition.

Crop rotation and drip irrigation use less water and little or no artificial fertilizer. No-till farming — a way of growing crops or pasture without disturbing the soil through tillage — could boost maize yields by 20 percent, and when combined with sustainable irrigation practices could bring the increase close to 70 percent.

Some of the new farming technologies employed by American farmers are exhibited at the 2015 Milan Expo’s U.S. Pavillion.

Farmer at the center

Sustainable agriculature can benefit farmers. Higher yields and lower fertilizer and pesticide cost mean higher income, and less exposure to harmful chemicals.

But farmers sometimes fear change, lack money or sufficient information, or distrust strangers telling them what to do. Farmer cooperatives and farmer field schools — networks for sharing ideas and knowledge — can help promote sustainable practices. Government officials can make it easier for farmers to make the switch.

When a Vietnamese official promoted the System of Rice Intensification (SRI), the result was more rice from less fertilizer and water.

International programs like the United States’ Feed the Future work to develop targeted climate-smart technologies and methods. Even agribusinesses and food companies can do their part. Corporations such as the Campbell Soup Company and General Mills are adopting sustainable practices in their supply chains. In India, Coca-Cola and a local NGO boost drip irrigation and other sustainable practices by training and equipping mango farmers in the state of Andhra Pradesh.

Seeds of change

Research is a key to further gains. Project Catalyst promotes farmer-driven innovations that reduce pesticide and fertilizer runoff into Australia’s Great Barrier Reef lagoon. In sub-Saharan Africa, where some farmers can barely afford fertilizer, many now “microdose,” or measure precisely the nutrients needed for each seed hole. Their high-tech tool: a simple bottle cap.

Over the next decade, researchers expect to breed plant varieties that use less fertilizer and produce higher yields.

The greatest hope, says Cornell University’s Norman Uphoff, lies in better understanding the role that billions of microorganisms play in plant and soil fertility. “We need an equivalent of the Copernican revolution to utilize the potential of those microorganisms,” he says.