When Alexander von Humboldt traveled in Venezuela in 1800, he was told by locals about the rapidly falling water levels of Lake Valencia. He established a theory that connected deforestation, falling water levels and change of (micro-)climate. Expanding on this, he later predicted that man-made interventions would lead to irreversible climate change, limiting the chances of future generations. He was one of the first scientists not only interested in specific plants or animals or limited ecosystems, but who saw a worldwide, interconnected ecosystem with mankind as a (destructive) part of it.

From the very interesting book The Invention of Nature by Andrea Wulf:

In the midst of the valley and surrounded by mountains was Lake Valencia. About a dozen rocky islands dotted the lake, some large enough to pasture goats and to farm. At sunset thousands of herons, flamingos and wild ducks brought the sky alive as they flew across the lake to roost on the islands. It looked idyllic but, as the locals told Humboldt, the lake’s water levels were falling rapidly. […]

As Humboldt investigated, he concluded that the clearing of the surrounding forests […] had caused the falling water levels. [Planters] had felled trees to clear land, and with it the forest’s undergrowth – moss, brushwood and root systems – had disappeared, leaving the soils beneath exposed to the elements and incapable of water retention. […]

All this was ‘closely connected’, Humboldt concluded, because in the past the forests had shielded the soil from the sun and thereby diminished the evaporation of the moisture. It was here, at Lake Valencia, that Humboldt developed his idea of human-induced climate change. […]

At Lake Valencia, Humboldt began to understand deforestation in a wider context and projected his local analysis forward to warn that the agricultural techniques of his day could have devastating consequences. The action of humankind across the globe, he warned, could affect future generations. What he saw at Lake Valencia, he would see again and again – from Lombardy in Italy to southern Peru, and many decades later in Russia. As Humboldt described how humankind was changing the climate, he unwittingly became the father of the environmental movement.

Humboldt was the first to explain the fundamental functions of the forest for the ecosystem and climate: the trees’ ability to store water and to enrich the atmosphere with moisture, their protection of the soil, and their cooling effect. He also talked about the impact of trees on the climate through the release of oxygen. The effects of the human species’ intervention were already ‘incalculable’, Humboldt insisted, and could become catastrophic if they continued to disturb the world so ‘brutally’. […]

It was all an ecological chain reaction. ‘Everything,’ Humboldt later said, ‘is interaction and reciprocal’. […] Humankind, he warned, had the power to destroy the environment and the consequences could be catastrophic.

From today’s perspective, this is nothing extraordinary, of course. But at the very beginning of the 19th century, this broke with a man-centered view of the world and with the optimistic belief that any human intervention would always bring progress.

“Why did nobody listen to what I said?”

(Many thanks to my reader Rodrigo Perez Garcia for sending me this fascinating book! If you also want to show your appreciation for my blog, here is my wishlist of books. Thank you! – Hier geht es zur deutschen Fassung.)