New Delhi, June 8 -- The upcoming Colombian presidential election between Sen. Ivan Cepeda, an ally of President Gustavo Petro, and lawyer Abelardo de la Espriella, whom U.S. President Donald Trump has endorsed, is shaping up as a stark choice that could impact the future of the Amazon rainforest, fossil fuel development and the rights of Indigenous communities.

The June 21 runoff comes at a pivotal moment for Colombia, which under Petro emerged as one of the world's most vocal advocates for protecting the Amazon and transitioning away from oil, gas and coal, the main drivers of climate change.

Petro opposed new oil and gas exploration contracts, vowed not to pursue fracking, a technique used to extract oil and gas from underground rock...