Bolsonaro, who won 55 per cent of the vote in a run-off on Sunday, issued a series of campaign pledges that left many fearing for the future of the Amazon, known as 'the lungs of the planet.'
Environmentalists and rights groups reacted with dismay Monday to the victory in Brazil of president-elect Jair Bolsonaro, a far-right champion of agribusiness who has threatened to pull his country from the Paris climate accord.
Bolsonaro, who won 55 per cent of the vote in a run-off on Sunday, issued a series of campaign pledges that left many fearing for the future of the Amazon, known as "the lungs of the planet".
He promised to merge Brazil's agriculture and environment ministries into one, saying "we won't have any more fights" over ecological concerns on deforestation.
"It's all about downsizing government and getting it out of the way so investors and big agribusiness landowners and companies can come in and have a freer hand for more trashing of resources and indigenous rights," Victor Menotti, a former director of the International Forum on Globalization, told AFP.
Bolsonaro, a former army captain, also raised the prospect of building hydro-electric power stations in the Amazon that would greatly restrict water access and forcibly remove indigenous communities.
"If (Bolsonaro) decides to move forward with his pledges against the environment, indigenous peoples and the climate, his fellow citizens will be the biggest victims," said Carlos Rittl, executive secretary of the Brazilian Climate Observatory.
"To increase deforestation and greenhouse gas emissions is to leave each and everyone of us more vulnerable to an increasing risk of climate extremes."
May Boeve, executive director at climate NGO 350.org, warned that a Bolsonaro presidency posed "a real threat to human rights at home and a risk to the momentum for climate action abroad."
Deforestation is responsible for about a fifth of greenhouse gas emissions and intensifies global warming.
But more than two decades of UN-led efforts to curb the practice have largely failed, with Earth still losing a wooded area the size of Greece every year.
The Amazon itself is retreating to the tune of 52,000 square kilometres (20,000 square miles) -- equivalent to the area of Costa Rica -- each year, as agriculture giants saw down trees to make way for vast tracts on which to graze cattle or grow plants for food and cosmetic products.
Indigenous community fears
Bolsonaro, who openly admires Brazil's former military dictatorship and shocked many with his derogatory remarks on women, gays and blacks, remained vague about the environment during campaigning.
He stunned many observers in August by pledging to follow US President Donald Trump's lead and pull Brazil out of the 2015 Paris treaty on climate change, before backtracking days before the run-off.
The Paris deal aims to limit temperature rises to "well below" two degrees Celsius (36 Fahrenheit) above pre-industrial levels.
A major report this month highlighted the vital role forests must play in limiting the impact of greenhouse gas emissions as well as the crucial role of indigenous people in forest upkeep.
Bolsonaro said in February that he would not give up "one centimetre more" land to indigenous communities in Brazil -- home to around 60 per cent of the Amazon rainforest -- who are often threatened when standing up for their rights.
Brazil is already the deadliest place for environmentalists, which pressure group Global Witness recording 57 deaths of people protecting land there last year.
Its annual report on environmentalist deaths said Brazil was already "actively weakening the laws and institutions designed to protect land rights and indigenous peoples".
Boeve said she feared for the indigenous population as Bolsonaro forges ahead with his development-at-any-price approach.
"The poorest will be the hardest hit by unchecked climate change," she said.
"Poor and vulnerable communities in Brazil also suffer most from the activities that drive climate change –- like fossil fuel extraction, fracking, and deforestation."