The Wajapi live in the Amazon region of northern Brazil, near the border with French Guiana. They tell of how their ancestors had to leave their homes more than once because of overcrowding and unsustainable use of the environment. They describe their current home as their "third planet," sending a clear message about how the stress placed on nature has taken its toll -  and those know that are well placed to recognize the threats and respond to the challenge.

"The interesting thing about the Wajapi's statements is how they voice the concerns of a group that has been forced to move because too many people have exploited their natural resources," said Adriana Ramos of the Social and Environmental Institute Coordinator for Action (ISA), one of the leading non-governmental organizations working with indigenous groups in Brazil. "If we confronted the indigenous people without prejudice, we could have deepened our knowledge. But instead we are always waiting for Western science to confirm what they have been telling us for a long time."

The Brazilian Amazon covers five million square kilometres, or almost sixty percent of Brazil's total area. The green blanket has many faces, depending whether you are in the tropical rainforest or on the plains. And in reality, the forest is far from being monotonously green - and nor is it uninhabited. Over thirty million people live there, many in cities such as Manaus or Belém, and others clustered along the rivers and waterways, or, as with the rubber tappers, in the depths of the jungle. Heated debates underway between scientists and environmentalists revolve around the balancing act between the securing the region's economic development while safeguarding its biodiversity.

There are 419 indigenous areas in the Amazon region. The various peoples protect their own habitat. Recent deforestation surveys show that 6,624 square kilometres of forest were razed in the period from August 2016 to July 2017 but only two percent of this total happened in indigenous areas. More than three-quarters of indigenous deforestation is concentrated in ten regions close to major construction projects, including the huge hydropower plants of Santo Antônio and Jirau in the federal state of Rondônia, or the power plant of Belo Monte in the state of Pará.

These construction projects trigger population growth in their respective regions and generate money. They are also characterised by a lack of supervision - meaning that lumberjacks are able to intrude on indigenous land. It is estimated that there are over 200 indigenous peoples in Brazil, with a deep diversity of worldviews, languages and traditions. This vast archive of knowledge is rarely tapped into by the channels of traditional science. For some time the environmental institute ISA has been working towards knowledge exchange on climate change, bringing together twenty leaders from 17 ethnic groups.

So far, the groups' extensive knowledge has hardly impacted on the broader climate debate. "Indigenous people are called in to answer questions that whites have already asked," said Adriana Ramos. "But if we started out by listening to the experiences and the reality of life among the indigenous people, other views and other issues would be heard".

Ramos' comments are specifically directed at the UN's Intergovernmental panel on climate change (IPCC ). "If there was an exchange of knowledge with indigenous people within the IPCC, we would be much further ahead," she said, pointing out how indigenous people keep close tabs on evidence of climate change, tracking stocks of insects or fish, aware of harvests and soils.

The forest itself reflects the changes. In the period from 2005 to 2017, six extreme natural events were recorded in the Amazon region, including major droughts and severe floods. "We've never experienced that before," said climate researcher Carlos Nobre. In the past, droughts occurred about every twenty years. "These intervals gave the woods time to recover. Now the ecosystem has started to oscillate wildly, the balance has become fragile and we still do not know why."

In the Amazon, the after effects of the weather phenomenon El Niño, which has led to temperature changes in the Pacific, are still being felt. The ecosystem also suffers when the water temperature in the North Atlantic is higher than that of the South Atlantic. Natural changes are joined by man-made environmental impacts. Forest fires, for example, are increasing dramatically due to slash-and-burn agriculture. In September 2017, the Brazilian space agency INPE used satellites to reveal the true extent of the destruction of forest, recording the number of forest fires in Brazil over the last 25 years.

An up-to-date inventory shows that about twenty percent of the rainforest has already disappeared. In 2014, according to a study by Antonio Nobre, about 42 billion trees had already been destroyed by the continuous stream of new arrivals into the Amazon region over the last forty years. The destruction of the forest prevents the storage and transmission of moisture to other regions and interrupts the temperature regulation by the vegetation.

The direct impact on the southwest of the country, especially on São Paulo, requires further investigation, but it is already clear that the complex system of nature functions as a whole. If you intervene at one point, you feel the effect elsewhere.

Carlos Nobre said that Brazil has managed to reduce deforestation in the period from 2005 to 2014 through better surveillance. Brazilian legislation allows Amazonian landowners to clear twenty percent of their land and obliges them to keep eighty percent intact. Researchers, however, are increasingly in favour of a complete halt to deforestation in the country. "Deforestation is harmful, the country does not need any more open space," said Paulo Barreto, a researcher at the Institute of Humans and the Environment in the Amazon, Imazon.

A recent study shows that deforestation and slash and burn agriculture have a negative impact on human and animal health in the region, and that the absence of rainfall is damaging agriculture. Moreover, slash and burn also accounts for 26 percent of greenhouse gas emissions in Brazil. "Fighting deforestation in the Amazon is one of the simplest steps in moving to a low-carbon economy," Barreto says.

The current government of President Temer, however, provides scant scope for optimism. The forest surveillance system using satellite imagery is threatened by cuts while the resources available to the Ministry of the Environment were also slashed. "These cuts make it impossible to monitor the clearing in the Amazon region as they have been done over the past decades," argued environmental physicist Paulo Artaxo of the University of São Paulo. However, he is not surprised by this development: "The Brazilian parliament is dominated by representatives of the large landowners. They are working to systematically destroy all measures of deforestation in the Amazon."