Sustainable development is applied to just about everything from energy to clean water and economic

Sustainable development is applied to just about everything from energy to clean water and economic growth, and as a result it has become difficult to question either the basic assumptions behind it or the way the concept is put to use. This is especially true in agriculture, where sustainable development is often taken as the sole measure of progress without a proper appreciation of historical and cultural perspectives. To start with, it is important to remember that the nature of agriculture has changed markedly throughout history, and will continue to do so .medieval agriculture in northern Europe fed, clothed and sheltered a predominantly rural society with a much lower population density than it is today. It had minimal effect on biodiversity, and any pollution it caused was typically localized. In terms of energy use and the nutrients captured in the product it was relatively inefficient. Contrast this with farming since the start of the industrial revolution. Competition from overseas led farmers to specialize and increase yields. Throughout this period food became cheaper, safe and more reliable. However, these changes have also led to habitat(栖息地)loss and to diminishing biodiversity. What’s more, demand for animal products in developing countries is growing so fast that meeting it will require an extra 300 million tons of grain a year by 2050.yet the growth of cities and industry is reducing the amount of water available for agriculture in many regions.A. To B.medieval C. Contrast D. What’s E.yet F. All G.thiswill H. Instead I. What J. How K.By L.By M.By N.By O.A.Localised P.competition Q.the R.the S.They T.They U.They V.They W.A.It X.It Y.It Z.It [.To .To ].To ^.To

农业的可持续发展始终在历史变迁中寻找平衡。中世纪欧洲农业以自给自足为主，采用休耕制和粪肥施肥，虽对生物多样性影响小、污染局限于局部，但能源利用和养分捕获效率较低。工业革命后，海外竞争促使农民专业化并提高产量，食品变得更便宜、安全和可靠，却也导致栖息地丧失和生物多样性减少。如今，发展中国家对动物产品需求激增，预计到2050年每年需额外3亿吨谷物，而城市和工业发展又在许多地区减少了农业可用水量，这让21世纪农业面临全新挑战。

应对这些挑战，需重新审视可持续农业的定义与内涵。它是兼顾农业生产与环境保护的生产方式，要实现经济、社会和环境效益的协调统一，遵循生态系统、资源节约、环境保护和经济效益原则。我国农业可持续发展面临特殊困境，用全球9%的耕地养活近20%的人口，还饲养着全球一半的猪，导致化肥和农药使用量远超世界平均水平，农业面源污染严重。

城市化或许是破解困境的关键。与普遍认知不同，城市化若管理得当，可通过农村人口迁移释放大量耕地。中国农村建设用地总量远超城市，当城市化率从50%提升至70%甚至90%，农村宅基地复垦能使农田面积净增。据模拟，2050年我国城市化率达90%时，农田面积将增加5 - 8万平方公里，相当于半个浙江省的面积。复垦后的土地虽可能质量不如城市周边耕地，但面积增加足以抵消单产差异，预计能使全国粮食总产量提升4%。

城市化还能推动农地规模化经营，这是解决农业污染和效率问题的核心。当前我国小农经营模式，户均耕地不足0.64公顷且地块分散，难以实现机械化和现代化，导致化肥农药过量使用。研究表明，农地规模扩大10倍，化肥农药使用量可大幅下降，而产量基本保持不变，劳动生产率和农民收入则显著提高。规模化经营促进农民采用先进技术和固定投入，如无人机喷洒农药，一人一天可完成上千亩地作业，降低对劳动力依赖，同时提高资源利用效率。

当然，规模化并非“一刀切”。中国约86%的地区适合推行空间规模化，其余14%的丘陵山区可发展“第六产业”，通过一二三产业融合，如观光农业、特色种植等提高附加值。同时，要注重种养结合，在区域尺度上优化种植业和养殖业布局，据测算，此举可使养殖业废弃物循环效率提高35%。

实现这一愿景，需政策支持与制度创新。改革户籍制度，消除农民进城障碍，提供住房、教育、医疗等公共服务，降低城市生活成本。建立“氮信用体系”等经济激励机制，补贴采用绿色农业技术的农民，推广新型肥料和精准施肥技术。合理推进农村宅基地复垦，避免“合村并居”中的简单粗暴做法，确保农民利益不受损害。

农业可持续发展是动态过程，需摒弃传统与现代对立的思维。21世纪农业不应追求“零影响”，而要在权衡土地利用方式利弊中寻找最优解，综合考量能源消耗、环境成本、水纯净度、碳足迹和生物多样性等多重指标。未来农业发展，既要借鉴国际经验，又要立足中国国情，通过城市化、规模化、科技应用和制度创新，实现粮食安全与环境保护的协同发展，这需要政府、农民、企业和科研机构等多方共同努力，在历史变迁中书写农业可持续发展的新篇章。