Climate change affects the relationship between the Andes and the Amazon

With vanishing glaciers and two thirds of its population of 30 million concentrated on the arid Pacific coast, Peru is one of the most vulnerable nations on earth to climate change. Yet the Peruvian Amazon, the world’s fourth largest national territory of tropical rainforest, will also play a critical role as the climate crisis unfolds, both in the global efforts to mitigate carbon emissions from deforestation and in the environmental and social impacts of global warming nationally within Peru and further downriver in the Amazon basin. How, then, will climate change affect Peru’s vast rainforest?

While there are an increasing number of long-range forecasts for the future of the Brazilian rainforest under climate change – many of which predict gloomy scenarios of savannization and desertification for large swathes of the lower Amazon as the interaction between global warming and local deforestation acquires a momentum of its own, a so-called “tipping point” – the Peruvian rainforest has seen much less research. This comes despite the critical hydrological relationship between the Andes and the rainforest and the fact that the Andes-Amazon region, particularly in Bolivia, Ecuador and Peru, is widely viewed as the world’s most diverse biome. Nevertheless, a scientific consensus is beginning to emerge. And although the large-scale loss of forest cover predicted for some other parts of the Amazon is not anticipated in Peru, the impacts are, nevertheless, alarming.

”It is probable that there will be a series of changes so dramatic that we have not seen them before and that will lead to a different ecosystem,” says Jhan Carlo Espinoza, a climatologist and hydrologist at the Geophysical Institute of Peru. To understand how climate change will affect the Upper Amazon, the key factor may be precipitation in the Andes. Of the Amazon River’s total discharge into the Atlantic of approximately 200,000 cubic meters per second, almost 40% is run-off from the mountain range. More specifically, around 25,000 cubic meters per second comes from each of Peru and Bolivia, while Colombia contributes around 15,000 cubic meters per second and Ecuador around 10,000 cubic meters per second.

Under modeling carried out by SENAMHI, the National Meteorological and Hydrological Service of Peru, rainfall in the Andes-Amazon is expected to fall by up to 10% in large parts of the Peruvian Andes and Amazon by 2030, particularly in Peru’s northern mountains, and by up to 20% in some of the hardest-hit highland areas. It is worth noting that that decline is compared to current rainfall levels, which have already seen significant drops in recent decades, possibly due to climate change but also possibly related to natural cycles; precipitation in the Peruvian Amazon watershed, covering both the Andes and the rainforest, has so far fallen by approximately 15% in recent decades, according to Dr Espinoza. Paradoxically, the loss of Peru’s glaciers, which will hit communities in the mountains and on the Pacific coast hard, will have a negligible impact on the rainforest; most Andean glaciers run off to the west, and thus contribute just a fraction of one percentage point to the Amazon’s total volume.

Unexpectedly, scientists are now finding that these changes owe more to the changes in global temperature and climate patterns than to local or regional deforestation, which appears to have less influence over the total volume or location of rainfall in the Andes than previously thought. Although El Niño does play a role in some Amazonian weather patterns, for example coinciding with a major drought in 1998, the Andes, towering almost seven kilometers into the sky at their highest point, represent a massive barrier that largely separates the Pacific and Atlantic weather systems and hydrological cycles. In other words, climate throughout the Amazon, including even the cloudforests of the eastern Andes and the watersheds that maintain them higher up the mountain slopes is largely integrated with Atlantic rather than Pacific weather systems.

Droughts, Floods and Landslides

Much of this decline in precipitation is occurring during the dry season, from around June to November. Rather than a gradual, linear drop in rainfall, the dry season is becoming more intense, including record droughts such as those seen in 1995, 1998, 2005 and 2010. At the same time, rainfall in the wet season may become more intense and concentrated. “We are are going to see a series of spikes, an increase in extreme events,” says Eduardo Durand, Director of Climate Change, Desertification and Hydrological Resources, at Peru’s recently formed Ministry of the Environment. Significantly the four record droughts of the 1990s and 2000s all occurred towards the end of the period since monitoring began in Peru in 1969. While the 1998 drought was correlated to El Niño in the Pacific, the other three each appear to be connected to unusually high temperatures in the tropical Atlantic.

In practice, this will mean an increase in droughts, floods and landslides in the Andes-Amazon, with significant consequences downriver, and across the Amazon basin, for communities, local ecosystems and, more broadly, the climatic stability of the entire Amazon and its ability to act as a carbon sink. The 2005 drought, which was thought to have been a once-in-a-century event, has been calculated to have released 1.6 Gigatonnes of carbon into the atmosphere. Yet the 2010 drought, whose impact is still being estimated, is now thought to have been more intense.

Many species, of both flora and fauna, are unable to survive these droughts but even the individuals that are able to get through such extreme dry spells are also affected: Often the plants that do outlive the drought will lose their foliage, which then forms a vast tinderbox on the forest floor, raising both the likelihood and intensity of forest fires, a relative rarity in a healthy tropical rainforest. Even in scenarios where forest cover survives, such as that predicted for much of Peru, the character of the ecosystem changes and much of the rich biodiversity of the primary rainforest may be lost. The social impacts will be immense, especially in a region where waterways provide the principal means of transport. Last year, for example, the cities of Pucallpa and Iquitos, the latter the largest urban area in the Peruvian Amazon, were cut off from each other as river beds became bone dry.

Meanwhile, during the wet season, intense bouts of rainfall are expected to increase, leading to flooding and landslides. The latter is a particularly significant danger in Peru with its precipitous terrain and pattern of unregulated human settlements, often of recent Andean immigrants in highly inappropriate locations. The risk of a repeat of the Yungay disaster, when nearly 80,000 people were killed as a result of a landslide triggered by an earthquake in the Andean province of Ancash in 1970, is one that Peruvian planners must now take seriously. Says Mr Durand: “Our problem here is run-off. To the extent that there is deforestation in the higher areas, which is the area with the greatest population density in our Amazon, uncontrolled colonization, trees are removed to keep livestock or for agriculture, we run the risk of altering the natural rhythms of flooding, which is already being affected by climate change. For the lower rainforest, the problem is not one of rains but of the cycles of flooding. This rhythm is key for them.”

The Research Institute of the Peruvian Amazon is already focusing its climate change work on the development of better territorial zoning in the Andes and Amazon to avert future tragedies. “Peru is an important laboratory because it includes the entire hydrological cycle that could be affected by climate change, from the mountains of the Andes to the continental Amazon,” notes Luis Limachi, head of the Institute’s Climate Change and Territorial Development program.

Upriver and Downriver

The consequences will not be confined to the Upper Amazon, with a series of impacts likely to be felt downriver all the way to the Atlantic. On the one hand, the upper stretches of the watershed’s ability to absorb large quantities of rain and then release it gradually is expected to reduce. In a nutshell, this means that variations in water levels across the Amazon and its tributaries will increase, with many more sudden highs and lows, amplifying the risk of flooding. Currently, when there are particularly intense rains in the Upper Amazon and the Andes, high altitude grasslands in the mountain range, cloudforests below and lowland rainforest even further down absorb much of the moisture and then release it steadily over time, effectively regulating water levels as far as the Amazon basin. That capacity will be lost as climate change alters those ecosystems, leading to greater flooding risks across the length of the Amazon and its tributaries.

Another critical impact may be on soil quality. Precipitation in the Andes does not just provide the Amazon basin with nearly 40% of its water; that water also comes loaded with nutrient-rich sediments that help maintain both the forest ecosystem and agriculture far downriver, a key element in Amazonian ecosystems where the earth is frequently poor. Scientists believe that around half the sediments that reach the lower Amazon come from the Andes, with extreme rainfall accounting for a high proportion of that total. How an intensified cycle of dry-wet seasons, with spikes of extreme rain and drought, will interfere with that critical flow of sediments remains a little-studied area. However, it is one prominent example of how changes in the hydrological cycle between the Andes and the Amazon as a result of global warming may reach far beyond the actual flow of water as they impact the rainforest’s delicate balance.

Beyond the direct environmental impacts of climate change on the Andes-Amazon, there are also likely to be a series of indirect, social effects, which are likely to amplify the impacts on the Upper Amazon’s ecological balance. More than anything else, migration from impoverished communities in the sierra, struggling to cope with water shortages and a broader context of under-development, to the rainforest is likely to increase. This trend, already a significant phenomenon in Peru, can have potentially devastating ecological impacts. Many of the migrants, who typically come from altitudes higher than 3,000 meters above sea level, have no knowledge of tropical horticulture and engage in destructive practices such as non-traditional slash-and-burn agriculture or artisanal gold mining, using large quantities of mercury, a practice that is currently ravaging large areas of primary rainforest in the Madre de Dios region.

Political Will

These impacts are all likely to be compounded by strategic decisions taken by policy-makers in Lima who, historically, have shown little appreciation for the Amazon other than as a source of natural resources to be plundered ruthlessly for export. Massive new infrastructure projects such as the Energy Agreement with Brazil that will see a series of vast hydroelectric dams built in Peru´s lowland rainforest for the first time or the recently completed InterOceanic Highway, that links Peru´s Pacific ports with Brazil, will all have a major ecological footprints. Although he insists Lima´s political classes are gradually becoming more environmentally aware, Mr Durand acknowledges: “There is little understanding in Peru in general, her leaders, her politicians, even her academics regarding what the Amazonian ecosystem is.”

Whether the incoming government, following the second round of presidential elections in June, shows a greater awareness of the need for a sustainable strategy for the Amazon remains to be seen. Despite the efforts of Mr. Durand and his colleagues at the Ministry of Environment – which was only established in 2008 as a condition of a trade treaty with the United States – the outgoing administration of President Alan Garcia has a dismal record on environmental issues. And other government departments, especially the Ministries of Agriculture and of Energy and Mines, still play a much more central role in Peru´s major economic and infrastructure decisions than Mr Durand’s department. As extreme climatic events tighten their grip on the Andes-Amazon, policy-makers in Lima will eventually see the light. But for local communities in the Upper Amazon, and further downstream deep in the Brazilian rainforest, the time for climate adaptation is already upon them.


Simeon Tegel is a British journalist and environmentalist based in Peru.