Economo and his colleagues analysed genomes of ant populations from the Fijian archipelago gathered in recent decades and held in museum collections. From thousands of specimens, they used scientific methods to infer whether ant populations were growing or shrinking based on variations in DNA sequences among individuals.<\/p>\n
They found that 79% of Fiji\u2019s endemic ant species were in decline, with impacts beginning at the time of humans\u2019 arrival on the islands about 3,000 years ago and speeding up in the past 300 years \u2013 coinciding with European contact, global trade and the arrival of modern agriculture.<\/p>\n
For remote tropical islands where comprehensive historical observations are rare, understanding how insects have been harmed by human activities is hard to ascertain but critically important. Islands are hotspots of biodiversity because of their isolation. This also makes them especially vulnerable to extinctions.<\/p>\n
\u201cRemote oceanic islands like the Gal\u00e1pagos, Hawaii and Fiji harbour species that evolved in isolation and often have spectacular differences from their mainland relatives,\u201d Economo said.<\/p>\n
The research adds to a patchwork map of findings from the world\u2019s ecosystems. In Germany, the abundance of flying insects across 63 nature reserves has dropped by 75% in less than 30 years. In the US, beetle numbers have plummeted by 83% in 45 years, and about 15% of tiger beetle species there are in decline. Europe\u2019s grassland butterfly population has shrunk by 36% over the past decade.<\/p>\n
Insect populations are being hammered from all sides as habitat loss, pesticide use, climate breakdown and light pollution all add to the emptying out of the world\u2019s wetlands, forests and grasslands.<\/p>\n
\u201cWe need to look at insects in more places, with more methods, to understand what is happening to insects and other invertebrates,\u201d Economo said.<\/p>\n