Shortly before his 44th birthday, in December 1988, the Brazilian rubber tapper and environmental activist Chico Mendes predicted he would not live until Christmas. “At first,” he said, “I thought I was fighting to save rubber trees, then I thought I was fighting to save the Amazon rainforest. Now I realize I am fighting for humanity.”

Mendes had received death threats for years. The threats escalated when an aggressive rancher laid claim to a nearby forest reserve, where he intended to burn and level trees to create pasture for cattle. The rancher hired gunmen to prowl around Mendes’s neighborhood. Mendes publicly opposed the rancher, and continued to advocate for the human rights of the indigenous peoples of the Amazon basin, saying Brazil must save the most biodiverse forest in the world. Destroy it, he said, and we, the human race, will end up destroying ourselves.

Three days before Christmas, 1988, Mendes was shot dead by the rancher’s son.

It stunned the world.

The National Council of Rubber Tappers, reeling from the assassination, made a plea that the Amazon be preserved “for the whole Brazilian nation as part of its identity and self-esteem”. The council added: “This Alliance of the Peoples of the Forest – bringing together Indians, rubber tappers, and riverbank communities – embraces all efforts to protect and preserve this immense but fragile life-system that involves our forests, rivers, lakes and springs, the source of our wealth and the basis of our cultures and traditions.”

Since Mendes’s murder, nearly 1 million sq km of the Amazon, an area roughly the size of Texas and New Mexico combined, have been destroyed, primarily in Brazil, but also in Peru, Colombia, Venezuela, Suriname, Guyana, and French Guyana. That equates to an average of some 200,000 acres every day, or 40 football fields per minute. In Brazil alone, home to the greatest expanse of forest, the rate of loss has increased by more than 30%. The Amazon – historically a great carbon absorber, since trees take in carbon dioxide and release oxygen – now releases more carbon than it stores, which adds to, rather helps to reduce, our global climate crisis.

Deforestation rates decreased slightly from 2004 to 2012. But since then, they’re back on the rise, especially in the past couple of years, since Jair Bolsonaro became president of Brazil.

In 2018, as Bolsonaro campaigned as a patriotic man of the people, scientists predicted that once the Amazon lost more than 25% of its tree cover, it would become a drier ecosystem, all because deforestation changes weather patterns (due to how trees respire), which in turn reduces rainfall. Furthermore, as the forest becomes fragmented, areas surrounded by pastureland will lose species in a process biogeographers call “ecosystem decay.”

In short, the Amazon is dying. Entire genetic libraries and symphonies of species – trees, birds, reptiles, insects and more, eons in the making, fine-tuned by natural selection – are being wiped out to make room for methane-belching cows.

“Bolsonaro is a powerful supporter of agribusiness,” the Washington Post reported before he won the presidency, “and is likely to favor profits over preservation. [He] has chafed at foreign pressure to safeguard the Amazon rain forest and he served notice to international nonprofit groups such as the World Wildlife Fund that he will not tolerate their agendas in Brazil. He has also come out strongly against lands reserved for indigenous tribes.”

Writing in Mongabay, a science website, Thais Borges and Sue Branford reported in May 2019 that a “new manifesto by eight of Brazil’s past environment ministers … warn[s] that Bolsonaro’s draconian environmental policies, including the weakening of environmental licensing, plus sweeping illegal deforestation amnesties, could cause great economic harm to Brazil”.

Robert Walker, a quantitative geographer at the University of Florida’s Center for Latin American studies, has said that unless something unprecedented happens, he predicts that the greatest rain forest on earth will be wiped out by 2064.

If so, it will have taken local opportunists – armed with chainsaws, bulldozers, and chants of “land, land, land” – little more than a century to destroy a rain forest 10 million years old and composed of some 390bn trees. Perhaps then, in the hot, brutal and not-too-distant future, when historians chronicle humanity’s destruction of its own home planet, the killing of the Amazon will rank at or near the top. And all the reasons why it had to be done – so pressing at the time – will seem trite until, stripped away, two fundamental causes remain: ignorance and greed.

Enter Pope Francis, who is not afraid to set precedent. Together with the Archbishop of Canterbury Justin Welby and Orthodox Ecumenical Patriarch Patrick Bartholomew, the world’s three main Christian leaders recently issued “A Joint Message for the Protection of Creation,” asking Christians everywhere to “listen to the cry of the Earth”. This includes everyone, rich and poor, old and young, who must examine their behavior and pledge “meaningful sacrifices for the sake of the Earth which God has given us.” The three also implored world leaders scheduled to attend the United Nations Climate Conference (Cop 26) in Glasgow, which begins on 31 October, to make courageous – and necessary – choices.

If his health permits, Francis will take part in the Glasgow conference. Welby also plans to attend. Hopefully, soon thereafter, Francis, who is the first pope in history from the Americas, would visit Brazil, the world’s most populous Roman Catholic country. He’d walk into the Amazon, bless the forest – what remains of it – and ask the world to help turn the tide on Brazil’s reckless policies. Perhaps he could give a homily on Revelations 7:3: “Do not harm the earth, the sea, or the trees…” One that inspires South Americans to improve their livelihoods while also protecting their ancient forest – the lungs of the earth. Finally, Francis could appeal to his church and the world’s richest nations to spend some of their vast wealth to help re-educate, re-tool, and re-employ the farmers, ranchers, squatters and businessfolk of the Amazon.

Soon after he was elected pope in 2013, Jorge Mario Bergoglio of Buenos Aires took his papal title after St Francis of Assisi of Italy, the patron saint of animals and birds, who, like Chico Mendes, died at 44, and spoke truth to power. Henry David Thoreau, the New England transcendentalist who wrote Walden and Civil Disobedience, also died at 44, and did the same.

It’s not how much time we have, or money. It’s what we do with it. “Let your life be a counter-friction to stop the machine,” Thoreau wrote. He added that whenever he walked in the woods, he came out “taller than the trees.”

Brazil takes its name from a tree, the Paubrasilia, so-given by Portuguese explorers who prized it for its red dyes. Known today as Pernambuco or brazilwood, it’s listed as an endangered species, and is carefully planted and managed, and selectively harvested by skilled men who, with machetes hanging from their rope belts, move through the forest like water, and often bless each tree before cutting the wood that will be carved into exquisite bows for violins, violas and cellos.

It’s said that the people of Brazil, no matter how difficult their situation, will smile rather than cry because they love life. It’s also been said that the future of Brazil is the future of the world.

Chico Mendes was right.

Save the Amazon, and we just might save ourselves.

• A frequent contributor to the Guardian, Kim Heacox is the author of many books, including The Only Kayak, a memoir, and Jimmy Bluefeather, a memoir, both winners of the National Outdoor Book Award. He lives in Alaska