Jair Bolsonaro’s rise to power in Brazil has cast a shadow over the first global environment conference since the ultra-nationalist was elected to lead the most biodiverse nation on Earth.

Participants at the the UN Convention on Biological Diversity, which opened in Sharm el-Sheikh on Saturday, expressed concerns that the former army captain would disrupt international efforts to prevent the collapse of natural life support systems in the same way that Donald Trump is undermining cooperation to stabilise the climate.

Bolsonaro will not enter office until January, but he has supported a weakening of protections for the Amazon, the richest area of biodiversity in the world. This would mean that less land is controlled by indigenous and forest communities and more is open to agribusiness, miners, loggers and construction companies. Much of his support during the election came from these interests.

This move is likely to put him on a collision course with the UN Convention on Biological Diversity, which aims to draw up a new deal for nature by 2020 that would halt and reverse the worst decline of life since the extinction of dinosaurs. Every nation except the US is a signatory.

Marco Lambertini, the head of WWF, said he hoped Bolsonaro would look at the bigger picture once he takes office. “Some of his statements are worrying, but we don’t want to prejudge. Politicians often say one thing in a campaign and another when faced with the reality of holding power. We’ll wait and see,” he said.

Lambertini added that the risks facing the Amazon were enormous. “This is an ecosystem that is fundamental for the whole world. Research papers have shown the loss of another 20% of the forest would be super-dangerous, pushing the Amazon past the point of no return so it would no longer be a rainforest but a savannah. This would affect rainfall patterns far beyond Brazil’s borders.”

He said that has faith in the Brazilian public on the issue: “We have seen a huge level of support for biodiversity protection in Brazil. I don’t think people voted for Bolsonaro because of his environmental agenda.”

Lambertini also urged other countries to offer more support to Brazil because it is home to a disproportionately large area of vital ecosystems such as the Amazon and the Cerrado.

UN officials and country delegates were reluctant to publicly comment on the incoming leader. However, several expressed fears off the record about what would happen to forest protection, indigenous rights and already weak global action to support the world’s natural infrastructure.

Delegates have bombarded the Brazilian participants with questions and sympathy, knowing that Bolsonaro has previously decried environmentalists, saying on one occasion: “This cowardly business of international NGOs like WWF and so many others from England sticking their noses into Brazil is going to end! This tomfoolery stops right here!”

The official delegation is wary of commenting during the transition period. They will be announcing a huge new demarcation of marine protected areas on Monday. That would normally be an achievement to celebrate, but lack of clarity about the future may mean a more muted mood.

Bolsonaro was once penalised for fishing in protected waters and has expressed his fury about this. The president-elect’s environment ministry transition team includes four military officers and the head of the agribusiness lobby, and priorities are likely to shift.

Biologists say Brazil is the world’s most biodiverse nation. Although it covers only 5.6% of the Earth’s land, it is home to 20.8% of plant species, 17.6% of birds, 13.6% of amphibians and 11.8% of mammals. No figure is available for insects but this proportion is likely to be even higher.

The country has been a key player in global climate and biodiversity talks and by cutting deforestation rates, it has set an example of what can be achieved. It has also helped bridge the diplomatic gap between wealthier and poorer countries to secure international agreements such as the 2015 Paris climate agreement and the 2010 Nagoya Protocol.

Marcel Kok, the international biodiversity programme leader at the Netherlands Environmental Assessment Agency, said world politics was shifting in a direction that made it harder to take concerted global action.

Kok told delegates at a side event: “If we compare the situation to 2010, it has become much more difficult to get international cooperation, due to the rise of populism and nationalism.”

Brazil’s position will become clearer in the coming months. Bolsonaro is expected to select a new minister for the weakened environment portfolio in the next few days. He recently chose Ernesto Araújo to become Brazil’s foreign minister. Araújo believes that international efforts to solve global problems are part of a cultural Marxist plot to curb growth in western economies and promote the rise of China.