As countries’ human life expectancy grows, so do their numbers of invasive and endangered species, according to a new study by University of California, Davis researchers.
The researchers examined social, economic and ecological information for 100 countries to determine which factors are most strongly linked to endangered and invasive birds and mammals. Human life expectancy is rarely included in such studies but turned out to be the best predictor of invasions and endangerment in these countries, according to the study published in Ecology and Society.
“Increased life expectancy means that people live longer and affect the planet longer; each year is another year of carbon footprint, ecological footprint, use of natural resources, etc. The magnitude of this impact is increased as more people live longer,” the authors wrote.
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New Zealand, Australia, Indonesia, the Philippines and the United States had the highest percentages of birds and mammals that are endangered and invasive. They also rank among those with the highest human life expectancy.
New Zealand had the most birds and mammals at risk of extinction – more than 40 percent, at least double the rate of other countries in the study. The authors said this “crisis may be due in large part to its isolation, high endemism, and recent human colonization.”
“New Zealand has had a massive invasion by nonindigenous species since its human colonization in the past 700 to 800 years, and this has resulted in catastrophic biodiversity loss,” they wrote.
African countries – 26 were included in the study – had the lowest percentage of invasive and endangered birds and mammals.
For each country, the researchers examined economic variables (per capita gross domestic product, export/import ratios, tourism, malnutrition, energy efficiency), ecological variables (agriculture, rainfall, water stress, wilderness protection, total biodiversity) and social variables (life expectancy, adult literacy, pesticide regulation, political stability, female participation in government). The 100 countries have about 87 percent of the world’s population, and comprise 74 percent of the Earth’s total land area.
Human activity has spurred more changes in biodiversity in the past 50 years than in the “whole of prior recorded human history,” the authors wrote.
Worldwide, 52 percent of cycads, 32 percent of amphibians, 25 percent of conifers, 23 percent of mammals and 12 percent of bird species are threatened with extinction, according to the 2005 Millennium Ecosystem Assessment.
The study also found that as a country’s per capita GDP increased, so did the percentage of invasive birds and mammals. And as biodiversity and total land area increased, so did the percentage of endangered birds. Pesticide regulations had no apparent link to numbers of endangered or invasive species.
This article originally ran at Environmental Health News, a news source published by Environmental Health Sciences, a nonprofit media company.