Vanishing Insect Populations Threaten Costa Rica’s Tropical Paradise

“Thanks for coming to see our all our bugs,” Daniel Janzen and Winifred Hallwachs wrote to me on the dedication page of their book 100 Caterpillars, published in 2006. Little did I know this dedication would later take on a somber significance.

In 2011, I was researching the Área de Conservación Guanacaste (ACG) in northwestern Costa Rica, a vast nature restoration site encompassing multiple ecosystems. While the park is renowned for its biodiversity, the presence of insects is crucial for its ecosystem’s health. Now, a decade later, Janzen and Hallwachs are issuing dire warnings about the park’s insect populations.

Catastrophic Insect Crashes: A Sign of Climate Change

Janzen and Hallwachs report significant population crashes—up to 80% in species richness and biomass—among spiders and insects, including caterpillars, in the reserve’s tropical dry forest. They attribute these crashes directly to climate change.

Vertiginous declines in insect populations have been observed worldwide. A groundbreaking 2018 report highlighted a 75% decrease in flying insect populations across 63 nature reserves in Germany over 27 years. What is happening in ACG suggests a broader, global issue.

The Unmatched Biodiversity of ACG

The ACG is unique for its vast range of ecosystems: 1,690 square kilometers of dry tropical forest, tropical rainforest, cloud forest, volcanic summits, and an entire Pacific coastal and marine reserve.

Its biodiversity is unparalleled compared to the northern hemisphere. According to Janzen, “There are as many species within 50 kilometers of our [forest] dwelling in northwestern Costa Rica as in all Europe or half of North America.”

The Severity of Population Crashes

Insect crashes in ACG have severe implications for overall biodiversity. The rainy season, once regular and predictable, now fluctuates by months. The intense dry season has increased from four to six months, leading to devastating effects.

Forests that were once rich with signs of insect activity, such as foliage consumption, nests, and eggs, now appear “fumigated,” with scarce evidence of life.

Janzen and Hallwachs assert that, “We are losing most of the insect community in the cloud forests due to the drying of the tops of tropical mountains, just as we are losing the huge biomass of insect communities that once occupied the fertile soils, weather, and water of the lowland tropics.”

The Need for Innovative Solutions

Janzen and Hallwachs advocate an innovative approach to addressing the declining insect populations. Central to their strategy is involving local communities in conservation efforts and biodiversity studies.

Since the park’s inception, residents have been trained as “parataxonomists” to collect, identify, and monitor insects. This dual approach not only enhances scientific knowledge but also instills a sense of pride and ownership in the community.

Janzen and Hallwachs argue that unless citizens worldwide treat wild nature with the same respect as their gardens, wildlands have no future. They propose seeing rich biodiversity as essential for human survival, not separate to be preserved solely for its own sake.

A Model for Change

The BioAlfa programme, initiated in Costa Rica, integrates biological literacy into the education system. Schools participated in trapping insects, which were sent to a barcoding facility for identification. Some of the species discovered were previously unknown to science.

Tragically, the BioAlfa project faced a setback in 2022 with the election of President Rodrigo Chaves, who has taken the country in an anti-environmental direction. Despite this, the project continues within the ACG.

Janzen and Hallwachs believe their approach can “reinforce a national attitude that is willing to keep its carbon out of the air, grow forest back on lands that once were cattle pastures, and keep its natural wild capital alive.”

Lessons for Ireland and Beyond

The potential loss of insect populations is having drastic, often undetected, negative impacts on natural systems worldwide. The National Biodiversity Data Centre in Ireland admits that monitoring of insect populations is still in its infancy.

Perhaps it is time to embrace the philosophy that Janzen and Hallwachs champion: recognizing and valuing the natural world as an integral part of our human heritage.

As we face the growing challenge of climate change, it is crucial to learn from these pioneers and take steps to preserve the natural world, including its most intricate inhabitants: the insects.

Paddy Woodworth’s book Our Once and Future