土壤侵蚀如何威胁我们的粮食和农业未来

风和水的侵蚀每年夺走我们国家农场数十亿吨的土壤. 事实上, US farms are currently losing twice as much topsoil to erosion per year as the Great Plains lost in a typical year at the height of the 1930s Dust Bowl, 这是我国历史上最具破坏性的农业和社会灾难之一.

这对我们的食品和农业的未来意味着什么? 我们对2020年的分析， 侵蚀未来，显示了继续我们目前的道路可能会威胁到我们所知道的农业. 而617888九五至尊娱乐变化的影响将放大这一威胁.

The good news is that the same innovative farming practices that can help make our farms more resilient to 617888九五至尊娱乐变化 can also slow the pace of soil loss. It's vitally important that we shift our nation's farm policies to support farmers in adopting these practices.

什么是健康的土壤——为什么它很重要

Soil is a living community—an enormously complex ecosystem in which the intersecting activities of plants, 动物, and microorganisms like fungi and bacteria combine to create a rich environment for food production.

健康土壤的特点是多孔性, “海绵”结构, produced by root growth as well as the activities of invertebrates such as earthworms and insects. 这种海绵性使雨水能够深入渗透健康的土壤, 使其不容易受到洪水和干旱的影响，因为更多的水下降 on 它会保持 in it.

健康的土壤不仅使农场更能适应617888九五至尊娱乐变化, 它们还可以通过多种方式帮助农民和纳税人降低成本:

• 减少了对昂贵的氮肥的需求, 两者都是因为健康的土壤一开始就富含养分, 因为更好的保水性意味着更少的肥料流失到径流中.
• 更少的肥料径流意味着更少的水污染, which reduces cleanup costs for public water supplies and recreation areas downstream from farm areas.
• 甚至更下游的地方, less runoff means a reduction in the algae blooms that annually turn huge areas of waterways like the Gulf of Mexico and Chesapeake Bay into “dead zones”, 严重破坏渔业.

土壤侵蚀:成因与影响

Erosion occurs when soil is displaced by wind or water—washed off farms and deposited in ditches and streams, 或是被风吹成尘土.

健康的土壤能很好地抵抗侵蚀, especially if it is protected by plants above ground and roots below-ground year-round (which is one of the reasons why 覆盖作物 是如此重要).

但是当土壤变得光秃秃的，受到破坏和枯竭——干燥, 压实, 而且有机物质含量低，风和水更容易取代它. 结果可能是灾难性的, 正如美国中部大平原地区在20世纪30年代发现的那样. 但即使是年复一年的小变化也会逐渐引起大问题.

沙尘暴和它的遗产

在20世纪最初的几十年里, 农民们在整个大平原上大幅扩展了不可持续的放牧和农业. 特别是, farmers encouraged by rising wheat prices in the 1910s and 1920s plowed up millions of acres of deep-rooted native grasses and adopted farming methods that made the soil a sitting duck for erosion. 晚些时候, 当时正值大萧条，小麦价格下跌, 绝望的农民开垦了更多的草地.

然后, 从1930年开始, 一段持续的严重干旱开始了, 把光, 退化的土壤任由该地区的大风摆布. 由此产生的沙尘暴带来了广泛的破坏, 农场破产，迫使大约400家,000人迁移. 在接下来的几十年里，大平原的一些地区一直人口稀少，经济萧条.

为应对这一生态灾难所采取的诸多措施之一, 联邦政府采取措施加强水土保持，防止水土流失, 包括建立土壤保持处, which still exists today as the Natural Resources Conservation Service (NRCS) of the US Department of Agriculture.

今天的土壤侵蚀

联邦政府对沙尘暴的反应, 还有其他因素，比如灌溉技术的进步, 阻止了如此明显的灾难再次发生. 但侵蚀仍然是严重的长期威胁, 因为风和水带走土壤的速度比土壤再生的速度还要快.

While erosion rates have recently declined somewhat since consistent measurements began in 1982, 土壤流失的速度继续威胁着农业遗产. 这些侵蚀率是其中一个原因, 1982年至2015年, 基本农田面积减少了25%.800万英亩——大致相当于俄亥俄州的面积.

除了, 未来几十年，617888九五至尊娱乐变化可能会加剧侵蚀的影响, 由于洪水和干旱预计将在全国大部分农田变得更加严重.

土壤的未来处于平衡状态:预测侵蚀损失

美国农民能期望未来的土壤是什么样子? We developed projections for soil erosion over the next 15 years (to 2035) and the next 80 years (to 2100), 使用三种场景:

• 途径1:一切照旧. 在这种情况下, 我们假设侵蚀率将按照目前报告的全国平均水平进行.
• 途径2:侵蚀加剧. 在这种情况下, we considered the possibility that erosion rates could increase back to their 1982 levels (the highest levels reported in the National Resources Inventory) over the next 15 years, 由于更具破坏性的土地管理实践的结合, 土地利用变化, 617888九五至尊娱乐变化加剧了侵蚀率.
• 途径3:减少侵蚀. 对于这种情况, we considered the possibility that increased use of soil health practices could reduce erosion rates by a national average equivalent to the amount reduced 1982年至2015年 over the course of the next 15 years.

We then extended the projected erosion rates from 2015 to 2100—a century after the initial 1982 measurements—to explore the accumulating impacts of different erosion rates over time.

The results of these projections show that cumulative average soil loss on US cropland by 2100 could range anywhere from about 2.5英寸到5英寸以上，正常情况下的预测是4英寸左右. 通过比较, farm soil in Iowa currently averages about 8 inches deep—and that's down from a historical depth of 12 to 14 inches.

简而言之，我们正走在一条危险而不可持续的道路上.

重建土壤:我们能做的

The good news is that we know how to slow down erosion and get our food and farm system back on a sustainable track. 关键是扩大农业实践，建立和保持更健康的土壤. 农民可以使用几种具体的策略来做到这一点:

植物覆盖作物. 通过常年把根埋在地里, 覆盖作物有助于保持土壤的位置，并最大限度地提高其保水能力, 使其更能抵抗洪水和干旱.

作物轮作多样化 帮助提高土壤肥力，破坏害虫循环.

多年生植物, 如草原草或树木, 在农田内或农田附近，常年保持深层根系，稳定土壤, 将碳拉入更深的地下, 并在多余的肥料成为污染物之前将其捕获.

少耕地(或者根本不耕地) 采用低耕或免耕耕作制度，尽量减少干扰，保持土壤水分.

虽然全国各地的许多农民已经在做一些或全部这些事情, 为他人, 采用这样的做法将是他们操作上的重大改变——而改变并不容易. It's in everybody's interest to support US farmers in rebuilding soil health and preventing erosion through policies, 比如《617888九五至尊娱乐》, 这可以确保一个对所有人都有利的过渡.