北美鸟类种群正在加速缩减。归因于气候变化和农业

Source: Slashdot

Overview

“北美上空飞行的鸟类数量比数十年前少了数十亿只，”美联社报道，“它们的种群正以更快的速度缩减，主要原因是密集农业和气温升高的综合作用，一项新研究发现。”

Key Findings

• Scope of the study: Researchers examined 261 bird species.
• Statistically significant declines: Nearly half of the species showed losses large enough to be statistically significant.
• Accelerating declines: More than half of the declining species have seen their losses accelerate since 1987, according to the journal Science (Thursday’s issue) — doi:10.1126/science.ads0871.
• Species not yet at risk of extinction: The fastest‑shrinking populations are those of common birds such as the European starling, American crow, grackle, and house sparrow. Their large numbers mean they are not currently considered at risk of extinction, said study lead author François Leroy, an Ohio State ecologist.

Geographic Patterns

• Southern regions experienced larger absolute population declines.
• Climate connection: A deeper statistical analysis linked these declines to warmer temperatures caused by human‑driven climate change. As co‑author Marta Jarzyna (Ohio State University) explained, “In regions where temperatures increase the most, we are seeing strongest declines in populations.”

Role of Agriculture

• Acceleration driver: While climate change explains the magnitude of declines, the acceleration of those declines is “mostly driven by agricultural practices,” according to Jarzyna.
• Correlated factors: The study found statistical correlations between faster decline rates and:
  • High fertilizer use
  • High pesticide use
  • Extent of cropland

Leroy cautioned that the study cannot prove causation, but the patterns “indicate agriculture in general is a factor.” He added, “The stronger the agriculture, the faster we will lose birds.”

Expert Commentary

• David Bird, wildlife biologist at McGill University (not involved in the study), praised the research methodology and its conclusions. He noted that growing human populations intensify agriculture, converting bird habitats to cropland, and that modern machinery can destroy nests and eggs.
• Insect decline link: Bird highlighted the broader “war on insects,” citing recent studies showing insect populations have crashed by over 40 % in many regions, including the United States. Many of the birds identified in the new study rely heavily on insects for food. (See the AP article on insect declines — link.)

Historical Context

A 2019 study by Cornell University conservation scientist Kenneth Rosenberg reported that North America had 3 billion fewer birds than in 1970. The article detailing that finding can be read here: AP News, 2019 study.