Insect collapse: ‘We are destroying our life support systems’

El Yunque national forest in Sierra de Luquillo, Puerto Rico. Photograph: Stuart Westmorland/Corbis/Getty Images

The Guardian has an article that highlights the collapsing rainforest ecosystem within Puerto Rico’s Luquillo rainforest.

You can find the article here …

Scientist Brad Lister returned to Puerto Rican rainforest after 35 years to find 98% of ground insects had vanished

“We knew that something was amiss in the first couple days,” said Brad Lister. “We were driving into the forest and at the same time both Andres and I said: ‘Where are all the birds?’ There was nothing.”

His return to the Luquillo rainforest in Puerto Rico after 35 years was to reveal an appalling discovery. The insect population that once provided plentiful food for birds throughout the mountainous national park had collapsed. On the ground, 98% had gone. Up in the leafy canopy, 80% had vanished. The most likely culprit by far is global warming.

“It was just astonishing,” Lister said. “Before, both the sticky ground plates and canopy plates would be covered with insects. You’d be there for hours picking them off the plates at night. But now the plates would come down after 12 hours in the tropical forest with a couple of lonely insects trapped or none at all.”

“It was a true collapse of the insect populations in that rainforest,” he said. “We began to realise this is terrible – a very, very disturbing result.”

It is not just a Guardian article he wrote it all up and published the precise details within the peer-reviewed journal PNAS.

Study: Climate-driven declines in arthropod abundance restructure a rainforest food web

Published in the Proceedings of the National Academy of Sciences (PNAS) journal on 15th Oct, it lays out the rather stark details …

  • Arthropods, invertebrates including insects that have external skeletons, are declining at an alarming rate.
  • They compared arthropod biomass in Puerto Rico’s Luquillo rainforest with data taken during the 1970s and found that biomass had fallen 10 to 60 times.
  • This has a knock on effect because for other species these are a food source – there has been synchronous declines in the lizards, frogs, and birds that eat arthropods.

Is this really due to Climate Change?

The Guardian article states that … “The most likely culprit by far is global warming“, so let’s ponder over that a bit by extracting a few observations examined within the paper published last Oct


Nope …

Given its long-term protected status, significant human perturbations have been virtually nonexistent within the Luquillo forest since the 1930s, and thus are an unlikely source of invertebrate declines.

Faming and pesticides

Nope …

Due to the ongoing reduction in agriculture and associated farmland, pesticides use in Puerto Rico also fell up to 80% between 1969 and 2012. Most pesticides have half-lives measured in days, not decades, making it improbable that, despite precipitous declines in their use, remaining residues are responsible for waning arthropod abundance.

It is just this one Rainforest and is not global

Nope …

Long-term abundance data taken by Pounds et al., Whitfield et al., and Stapley et al. indicate that Anolis populations in other tropical forests have declined in parallel with anoles at Luquillo. At Monteverde, Costa Rica, populations of Anolis tropidolepis and Anolis altae were diminishing by 4.4% and 3.1% per year, respectively, for 11 and 13 y before both species became locally extinct. Over a 35-y period at La Selva, Costa Rica, Anolis capito, Anolis humilis, and Anolis apletophallus decreased by 23%, 78%, and 71%, respectively, and in the rainforest on Barro Colorado Island, Panama, A. apletophallusabundance declined by 71% between 1971 and 2011. Proposed drivers of these trends were reduced mist frequency at Monteverde, diminished leaf litter due to climate change at La Selva, and the effects of the ENSO combined with a rise in minimum temperatures on Barro Colorado.

Brad Lister Quotes

Beyond that initial study last Oct, here are a few additional observations that he makes within this latest Guardian article that highlights it all …

…“We are essentially destroying the very life support systems that allow us to sustain our existence on the planet, along with all the other life on the planet,” Lister said. “It is just horrifying to watch us decimate the natural world like this.”…

…“It was and still is the most beautiful forest I have ever been in. It’s almost enchanted. There’s the lush verdant forest and cascading waterfalls, and along the roadsides there are carpets of multicoloured flowers. It’s a phantasmagoric landscape.”….

…“One of the things I noticed in the forest was a lack of butterflies,” he said. “They used to be all along the roadside, especially after the rain stopped, hundreds upon hundreds of them. But we couldn’t see one butterfly.”…

….”it’s all connected and when the invertebrates are declining the entire food web is going to suffer and degrade. It is a system-wide effect.”


Hyper Alarming

Lister’s paper from last Oct concludes as follows …

Our analyses provide strong support for the hypothesis that climate warming has been a major factor driving reductions in arthropod abundance, and that these declines have in turn precipitated decreases in forest insectivores in a classic bottom-up cascade. This hypothesis also provides a parsimonious explanation for why similar cross-taxa, concordant decreases in reptiles, anurans, and birds have occurred in Costa Rican rainforests, and are likely occurring across a broad range of tropical ecosystems. Overall, there is an urgent need for more widespread monitoring of arthropods and insectivores throughout the tropics. As the sixth mass extinction continues to decimate the world’s biota, these data will be crucial to understanding the impact of climate change on terrestrial food webs, ecosystem dynamics, and biodiversity, and to formulating conservation strategies aimed at mitigating the effects of future climate forcing.

The latest Guardian article not only points out that more data is needed because there have been very few few studies of insect numbers in past decades to serve as a baseline, but also drives the key point home with this one paragraph buried in the middle …

Earth’s bugs outweigh humans 17 times over and are such a fundamental foundation of the food chain that scientists say a crash in insect numbers risks ecological Armageddon. When Lister’s study was published in October, one expert called the findings “hyper-alarming”

Severe impacts from Climate Change are not located within some far and distant future, it is here now, and for this rainforest ecosystem it may already be too late.

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