Studies on insect populations in recent years show that the impact of climate change on tropical ecosystems may be much greater than had been anticipated.
The results are so dire that the findings prompted one researcher to concludethat “We are essentially destroying the very life support systems that allow us to sustain our existence on the planet.” Others have gone so far as to say that we are on course for ecological Armageddon.
A study published last year showed that in the Puerto Rican Luquillo rainforest, 98% of insects on the ground have disappeared over the past 35 years, while those that inhabit the leaf canopy above have declined by about 80%.
The numbers of frogs and birds that depend on the insects for at least part of their diet have dropped by 50-65% in that time period, and the number of birds that eat almost nothing but insects dropped by 90%. The abundance of fruit- and grain-eating birds was not affected.
The Luquillo rainforest is a protected area and has not been subjected to habitat disturbance or exposure to pesticides. The authors propose that the collapse of the insect population is being driven by climate warming and the tremendous increase in the number of hot spells over the past 40 years. While temperatures in Luquillo rarely exceeded 29C in the 1970s, about 44% of the days do so now..
This study is one of just a handful of assessments on insect populations globally. There has also been a drastic plunge in insects over the past 25 years in Germany’s natural reserves, while the virtual disappearance of birds from an Australian eucalyptus forest is also attributed to the loss of insects caused by heat and drought. In Mexico, insect numbers in a dry forest fell 80% since the 1980s. In addition to climate change, destruction of habitat and pesticide use are among the main causes of the global decline in insects. The authors of the Luquillo study note that the impact of various causal agents affecting insect declines in tropical and temperate regions may differ.
The Earth is losing its vertebrate and invertebrate wildlife at an alarming pace due to human activities: habitat loss, unsustainable hunting, invasive species, poaching, pollution and the heating of the planet. While extinction is a normal part of evolution, the current rate of extinction has greatly exceeded the historical background rate and shows no signs of slowing as human activities and appropriation of habitat continue apace.
A 2015 study estimated that the total number of vertebrate species that went extinct during the preceding century would have taken 800 to 10,000 years to disappear at the background rate. Even applying stringent assumptions to meet the requirement for a species to be considered extinct, the average rate of vertebrate species loss was up to 100 times higher than the background rate.
Conservation work and other efforts to mitigate the impact of humanity can perhaps avert a dramatic decay of biodiversity and loss of ecosystems, but without a concerted effort to stabilize and eventually reduce the human population, all such efforts are likely to fall far short of achieving a sustainable future.