After three hundred years of impressive gains in wealth and population, Europe’s economy began to slow around 1300. Several factors accounted for the decline. One the most important, though perhaps the least dramatic to relate, was a shift in climate. The remarkably fair weather of the twelfth and thirteenth centuries took a decided turn for the worse in the fourteenth. Chronicler’s comments, tree-ring examination, and pollen analysis all indicate that over the course of the fourteenth century Europe’s average annual temperature declined approximately two degrees Celsius—which may sound like very little at first, but if one considers current projections about the possible effects of global warming, in which the average annual temperature shift is only one degree Celsius, a rather different impression emerges. As the temperature dropped, shortening the summer growing season and affecting the resilience of certain vegetable species, the wind and rain increased. This meant that crop yields declined precipitously and the agricultural economy began to contract. As food supplies dwindled, costs rose accordingly and cut into the amount of capital that people had available for other purchases or investments. This in turn added to the gradual construction of the commercial economy.

Just as significant were changes in the geopolitics of the Mediterranean world. The decline of the Byzantine Empire, which had dominated the eastern Mediterranean, meant the interruption or trade routes to central and eastern Asia. The rise of new political powers signaled a new era in Mediterranean connections, one in which religious loyalty and ethnic fidelity mattered more than commercial ties. Consequently the movement of goods and services between east and west began to slow. European interest in circumnavigating Africa and exploring westward into the Atlantic Ocean, in fact, originated in the desire to avoid the roadblock in the eastern Mediterranean and to tap directly into the trade with eastern Asia that had long sustained Europe’s economic growth.

A more immediate cause of the sputtering economy was an observable absence: since the eleventh century there had been few significant changes in the technology of agriculture. Developments like the wheeled plow, the rotation of crops, and the use of natural fertilizer that had made possible the agricultural revolution of the past two hundred years had had no follow-up. Farming was still conducted in 1300 roughly the same way it had been done in 1100, but with a considerably larger population to feed, there was little surplus left to generate fresh capital. As a consequence, food production fell perilously close to subsistence level. Although the failure of agriculture to keep up with the growing population did not become a crisis until the fourteenth century, clear signs of the problem had already emerged by the middle of the thirteenth century, when occasionally low yields due to bad weather or social disruption revealed how perilous the balance between Europe’s population and its food supply had become. Apart from territories beset by war, the tentativeness of the food supply became evident first on the farmlands most recently brought under cultivation during the economic depression of the twelfth century. The less established farmers of these lands frequently did not have the means to survive successive poor harvests. Tenant farmers unable to pay their rents thus began to slip into debt, and landlords who depended on rents for their income began to rely increasingly on urban financiers for credit.

Even whole governments became entangled in the credit crisis, England being the most notable example. The cycle of indebtedness was hardly inevitable, but the string of bank failures and commercial collapses in the first half of the fourteenth century was striking. The famed Bardi and Peruzzi banks of Florence (the two largest financial houses of Europe) collapsed spectacularly in the 1340’s. They were soon followed by the Riccardi bank of Lucca, whose massive loans had kept the English government afloat for years. Many more houses collapsed in turn.

An important demographic trend resulted from and contributed to the economic malaise: large-scale migration of rural populations into the cities. Europe’s overall population growth from 1050 to 1300 had been primarily due to an increase in the number of rural folk. But as economic forces made agrarian life more perilous around 1300, hard-pressed farmers and their families began to migrate to the cities in large numbers in search of work. Many cities doubled in size, and some even tripled, over the course of just one or two generations. Few were capable of absorbing such large numbers of people.

在财富和人口经历了300年的惊人增长之后，1300年左右欧洲经济开始萧条。这种衰退是若干因素导致的。其中最重要的一个，也许是最不引人注目的是气候变化。十二和十三世纪的天气非常晴朗，而在十四世纪天气变得糟糕起来。编年史者的评论、树木年轮的检测和花粉的分析都表明，十四世纪欧洲的年平均气温下降了大约两摄氏度，起初听起来似乎很小，但是如果人们是根据当前的情况，考虑全球变暖可能带来的影响，平均每年温度变化只有一摄氏度，那么一个相当不同的印象就出现了。气温的下降缩短了夏季作物的生长季节，影响了某些蔬菜品种的弹性，大风和雨水都有所增加。这意味着农作物产量急剧下降，农业经济开始萎缩。随着食品供应的减少，成本相应上升，人们的其他购买或投资的资金量会有所削减。这反过来又促进了商业经济的逐步建设。 同样重要的是地中海地区地缘政治的变化。支配着地中海东部的拜占庭帝国的衰落意味着亚洲中部和东部贸易路线的中断。新的政治力量的崛起标志着地中海的新时代的到来，宗教忠诚和民族忠诚比商业联系更重要。因此，东西方之间的货物和服务流动开始放缓。事实上，欧洲对绕过非洲向西进入大西洋的兴趣，源于避免地中海东部路障，并直接与东亚进行贸易的渴望，这在长期以来一直维持着欧洲的经济增长。 经济增长缓慢的一个更直接的原因是可观测性的缺位：自十一世纪以来，农业技术的变化不大。像轮式犁、农作物轮作和对促成过去二百年农业革命的天然肥料的使用都没有发展的后续。1300年的农业仍然与1100年的大致相同，但由于人口相当庞大，所以可用于形成新鲜资本的剩余资金很少。因此，粮食生产岌岌可危，已经衰退到接近仅能维持生存的水平。尽管农业未能跟上不断增长的人口直到十四世纪才形成危机，但在十三世纪中旬已经出现了明显的迹象，当时由于恶劣天气或社会混乱造成低生产率，并表明了欧洲人口和粮食供应之间的平衡已经变得危险。除了受战争侵扰的领土之外，在十二世纪的经济萧条期间，粮食供应紧张一开始是在最近被耕种的农田上明显体现出来的。这些土地上较不成熟的农民常常没有足够的手段来维持连续的歉收。佃农们无力支付租金，于是开始负债，依靠租金为收入的房东们开始越来越多地依赖城市资本家贷款。 甚至整个政府都卷入了信贷危机，英国是最引人注目的例子。债务的循环几乎是不可避免的，但是十四世纪上半年的银行倒闭和商业崩盘是惊人的。佛罗伦萨著名的巴迪和佩鲁济银行（欧洲最大的两个金融机构）在1340年突然崩盘。很快随之而来的卢卡的里卡迪银行，其巨额贷款一直维持着英国政府多年来的运转。更多的房屋又倒塌了。 一个重要的人口趋势是导致经济不景气的原因：农村人口大规模迁移到城市。欧洲人口总数从1050年到1300年期间额增长主要是由于农村人口数量的增加。但随着经济条件在1300年左右使农村生活更加岌岌可危，经济困难的农民和他们的家庭开始大量迁移到城市寻找工作。许多城市的规模在一代或两代人的过程中增长至原来的两倍甚至三倍。很少城市能吸收容纳如此庞大的人口。