美国农场农作物多样性下降

美国农场农作物多样性下降

U.S. farmers are growing fewer types of crops than they were 34 years ago, which could have implications for how farms fare as changes to the climate evolve, according to a large-scale study by Kansas State University, North Dakota State University and the U.S. Department of Agriculture. Less crop diversity may also be impacting the general ecosystem1. "At the national level, crop diversity declined over the period we analyzed," said Jonathan Aguilar, K-State water resources engineer and lead researcher on the study.

The scientists used data from the USDA's U.S. Census3 of Agriculture, which is published every five years from information provided by U.S. farmers. The team studied data from 1978 through 2012 across the country's contiguous states.

Croplands comprise about 408 million acres (165 million hectares) or 22 percent of the total land base in the lower 48 states, so changes in crop species diversity could have a substantial impact, not only on agroecosystem function, but also the function of surrounding natural and urban areas. Because croplands are typically replanted annually4, theoretically crop species diversity can change fairly rapidly. There is the potential for swift positive change, unlike in natural ecosystems5.

Aguilar began the study while working as a researcher with the USDA's Agricultural Research Service. He joined K-State Research and Extension, a part of the university, in 2012. The study was conducted in collaboration6 with a diverse team, including rangelands expert John Hendrickson, USDA-ARS; weeds experts Greta Gramig, NDSU, and Frank Forcella, USDA-ARS; agricultural economics expert David Archer2, USDA-ARS; and soils expert Mark Liebig, USDA-ARS.

"At the very simplistic level," Aguilar said, "crop diversity is a measure of how many crops in an area could possibly work together to resist, address and adjust to potential widespread crop failures, including natural problems such as pests and diseases, weed pressures, droughts and flood events. This could also be viewed as a way to spread potential risks to a producer. Just like in the natural landscape, areas with high diversity tend to be more resilient to external pressures than are areas with low diversity. In other words, diversity provides stability in an area to assure food sustainability."

1 ecosystem

n.生态系统

参考例句：

This destroyed the ecosystem of the island.这样破坏了岛上的生态系统。

We all have an interest in maintaining the integrity of the ecosystem.维持生态系统的完整是我们共同的利益。

2 archer

n.射手，弓箭手

参考例句：

The archer strung his bow and aimed an arrow at the target.弓箭手拉紧弓弦将箭瞄准靶子。

The archer's shot was a perfect bull's-eye.射手的那一箭正中靶心。

3 census

n.(官方的)人口调查，人口普查

参考例句：

A census of population is taken every ten years.人口普查每10年进行一次。

The census is taken one time every four years in our country.我国每四年一次人口普查。

4 annually

adv.一年一次，每年

参考例句：

Many migratory birds visit this lake annually.许多候鸟每年到这个湖上作短期逗留。

They celebrate their wedding anniversary annually.他们每年庆祝一番结婚纪念日。

5 ecosystems

n.生态系统( ecosystem的名词复数 )

参考例句：

There are highly sensitive and delicately balanced ecosystems in the forest. 森林里有高度敏感、灵敏平衡的各种生态系统。 来自《简明英汉词典》

Madagascar's ecosystems range from rainforest to semi-desert. 马达加斯加生态系统类型多样，从雨林到半荒漠等不一而足。 来自辞典例句

6 collaboration

n.合作，协作；勾结

参考例句：

The two companies are working in close collaboration each other.这两家公司密切合作。

He was shot for collaboration with the enemy.他因通敌而被枪毙了。