The fires in the Amazon are a “true apocalypse”, according to a Brazilian archbishop who expects next month’s papal synod at the Vatican to strongly denounce the destruction of the rainforest.

The comments by Erwin Kräutler will put fresh pressure on the Brazilian president, Jair Bolsonaro, following criticism from G7 leaders last month over the surge of deforestation in the world’s biggest terrestrial carbon sink.

The archbishop’s words also highlight a widening division between the Catholic church and the Pentecostal movement. Pope Francis has championed a more harmonious relationship with the natural world for the sake of future generations, in contrast to the fast-growing new-world Pentecostalists who form the support base for the ramped-up resource exploitation advocated by Bolsonaro and Donald Trump.

The gathering of bishops would condemn all forms of Amazon destruction and advocate a new view of ecology based on Christian faith in God as the creator of a “common home”, Kräutler said in an email exchange with the Guardian. Although retired as a bishop of Xingu, he is one of 18 members of the preparatory council appointed by Francis ahead of next month’s papal synod on the Amazon.

Following the meeting, Francis is expected to reinforce this message with an “apostolic exhortation”. It is likely to build on his influential 180-page encyclical on climate change, Laudato Si’, published four years ago, which called for concrete steps to tackle the environmental crisis.

Quick Guide Amazon fires - what is happening and should we be concerned? Show What is happening in the Amazon? Thousands of fires are burning in Brazil, many of them in the world’s biggest rainforest. While this does happen every year, some areas have suffered far more than usual. In the worst-affected Brazilian state of Amazonas, the peak day for fires in August was 700% higher than the average for the same date over the past 15 years. In other states, the amount of ash and other particulates in the air in August has hit the highest level since 2010. What is the cause? Most of the fires are agricultural, either smallholders burning stubble after harvest, or farmers clearing forest for cropland. Illegal land-grabbers also destroy trees so they can raise the value of the property they seize. But they are manmade and mostly deliberate. Is the entire forest ablaze? No. Satellite monitoring experts say the images of an entire forest ablaze are exaggerated. A great deal of misinformation has been spread by social media, including the use of striking images from previous years’ burning seasons. This week, there are more large fires in Colombia and eastern Brazil than in the Amazon. Do we need to worry about oxygen? No. Although some reports have claimed the Amazon produces 20% of the world’s oxygen, it is not clear where this figure originated. The true figure is likely to be no more than 6%. Even if it were accurate, the crops being planted in the cleared forest areas would also produce oxygen. So although the burning of the rainforest is worrying for many reasons, there is no need to worry about an oxygen shortage. So should we still be concerned? Extremely. The fires are mostly illegal and they are degrading the world’s biggest terrestrial carbon sink and most important home for biodiversity. They also contribute to a more important trend, which is an alarming rise in deforestation. Scientists say the Amazon is approaching a tipping point, after which it will irreversibly degrade into a dry savannah. At a time when the world needs billions more trees to absorb carbon and stabilise the climate, the planet is losing its biggest rainforest. Jonathan Watts

Preparations for an Amazon synod have been under way since 2016, but the issue has become more urgent in recent months due to fires, threats and a hostile government, Kräutler said.

“There have always been fires in the Amazon. When they are smaller, nature rebuilds itself within a few years. But what you are seeing now is a true apocalypse,” said the archbishop, who has spent 54 years in the region.

“The fires this year surpass anything you can imagine. Undoubtedly, it is the consequence of comments by [Bolsonaro] about the opening of the Amazon to national and multinational companies. He understands ‘opening the Amazon’ as a licence to clear a rainforest and gain space for cattle to graze and plant monocultures such as soybeans and sugar cane.”

Earlier this week, Catholic clergy in the Amazon released an open letter condemning violence and intimidation they say they are experiencing as a result of efforts to protect the forest, indigenous people and poor communities from miners and farmers.

“We are deeply disappointed that today, instead of being supported and encouraged, our leaders are criminalised as enemies of the fatherland,” they wrote.

“Together with Pope Francis, we are uncompromisingly defending the Amazon and demanding urgent measures from governments in the face of violent and irrational aggression against nature and the destruction of the forest that kills ancient flora and fauna with criminal fires.”

Pope Francis has championed a more harmonious relationship with the natural world. Photograph: Grant Neuenburg/Reuters

Kräutler said the letter was necessary because the government had spread false rumours that the Catholic church was undermining Brazilian sovereignty.

Priests and nuns have a long history of working with poor communities in the Amazon, which has often put them at odds with powerful business interests and the authorities. During the 1970s, the Liberation theology movement was closely aligned with leftwing resistance to the military dictatorship of the time.

In 2005, the America nun Dorothy Stang was murdered by landowners. One of her followers, Father Amaro Lopes, was arrested last year in the Xingu River basin. Kräutler had so many death threats he needed police protection for more than 10 years.

Tensions have risen further since Bolsonaro – a former military officer who has defended the use of torture and killings during the 20-year dictatorship that ended in 1985 – became president.

He has weakened government protections of the rainforest, verbally attacked indigenous groups, accused environmental NGOs of starting fires and broken ties with foreign donors to the Amazon Fund. In July – when deforestation alerts jumped by 278% compared with the same month last year – he fired the head of the space agency that provided the data.

On Saturday, Bolsonaro confirmed that he wanted the Brazilian intelligence agency to conduct surveillance on the Amazon synod. “There is a lot of political influence there,” the president reportedly told journalists.

Although nominally a Catholic, Bolsonaro was baptised a few years ago by evangelical pastors in Israel. His rise to power has depended heavily on support from the Pentecostal movement, which is growing far more rapidly than the Catholic church.

Q&A Amazon fires - what can you do to help? Show With the Amazon rainforest being affected by forest fires and deforestations, here are some practical ways to help. The most important actions are political and collective. Join a party or campaign group that makes the Amazon a priority. Through these groups, urge your elected representatives to block trade deals with countries that destroy their forests and to provide more support for countries that expand tree cover. Apart from this, donate to organisations that support the forest, forest dwellers and biodiversity, including Instituto Socioambiental, Amazon Watch, WWF, Greenpeace, Imazon, International Rivers and Friends of the Earth. As consumers, think twice before buying Brazilian beef or other products unless certified by groups such as Rainforest Alliance. The Amazon connection is not always obvious.

Jonathan Watts

A primary goal of the synod is to increase the ability of the Catholic church to evangelise in the Amazon and – although unstated – to counter the rise of Pentecostalism, which tends to support resource exploitation and has made inroads among indigenous and riverine communities. But bishops have been hamstrung by the difficulty of finding priests willing to work in the remote region.

One of the more radical ideas in a preparatory document for the synod, Instrumentum Laboris, is to allow older married men to be ordained – a move which would end a centuries-old requirement that priests are celibate.

Francis has previously said he would be open to allowing married men to be ordained in areas where there is a scarcity of priests, but the idea is highly controversial among Vatican conservatives, with cardinals having described it as “heretical” and “apostasy”.

Instrumentum Laboris also laments the crisis in the Amazon, which it attributes to “secularisation, the throwaway culture and the idolatry of money”.

“Today the Amazon is wounded, its beauty deformed, a place of pain and violence,” it continues. “The manifold destruction of human and environmental life, the diseases and pollution of rivers and lands, the felling and burning of trees, the massive loss of biodiversity, the disappearance of species (more than 1m of the 8m animals and plants are at risk), constitute a brutal reality that challenges us all.

“Violence, chaos and corruption are rampant. The territory has become a space of discord and of extermination of peoples, cultures and generations.”