• What are the Amazonian rainforest types to be found in Loreto, Peru?

• What effect is climate change having on water levels here?

• How do these water levels impact fauna & humans?

• How can one be part of the research?

The shrinking of the vast Amazon basin, as trees are cut down to make way for mining and agriculture, urban areas expand and roads are built, is seen as one of the driving factors of climate change.

Equally, this climate change has an impact on Amazonia itself: in the last 20 years, it has been experiencing greater climatic fluctuations manifested by greater flooding during the rainy season and more severe droughts in the dry season.

In the Peruvian department of Loreto (whose capital is Iquitos), which makes up part of Western Amazonia, research is being conducted by FundAmazonia, a not-for-profit institution, as to how these changes are impacting wildlife, biodiversity, and the lives of indigenous people.

As a starting point, we should explain that the western Amazon forests can be broadly split into two categories:

1. Tierra firme: forests that remain unflooded throughout the year.

2. Flooded forest: that fluctuates annually between flooded (December - June) and dry (July - November) seasons.

To further muddy the waters [pun intended], flooded forest is sub-divided according to the origin of the water by which it is inundated:

1. ‘Whitewater’ rivers: despite their name, these are usually brown in colour. This is a result of the heavy sediment load in the water.

   Whitewater rivers rise in the Andes mountains, and accumulate sediment - that includes topsoil and minerals - as they descend.

   The forest areas that are flooded by whitewater rivers are known as varzea.

   When this flooding recedes, it leaves behind a lot of sediment, making the soil rich and good for agriculture.

2. ‘Blackwater’ rivers: these originate in lowland tropical forest, where the ancient soils have no minerals to increase the alkali content. Moreover, as they move slowly along the generally flat terrain of Amazonia, tannins are released from decaying leaves. These are acidic and giving the water a dark hue.  

   This acidic water, with a pH between 3.5 - 6, acts as a steriliser, keeping parasite and bacteria populations to a minimum, and inhibiting the proliferation of insect larvae. So, fewer mozzies … but also fewer animals (eg bats, birds) that feed on insects! 

   Forests flooded by blackwater are known as igapo … or ‘swamp forest’. Only trees that can tolerate acidity survive in these areas.

When these two river systems meet, the results can be visually impressive.

The best-known example of this is near the Brazilian city of Manaus, where the Rio Negro (a blackwater river, as the name suggests) meets the Rio Solimoes (a whitewater river, with its headwaters in the Peruvian Andes).

At the Meeting of the Waters, the contrasting colours are clearly visible, especially from the air; and it takes a further 8 km (5 miles) approximately for them to mix completely.

Flooded forests - of both the varzea and igapo types - cover roughly 375,000 square km (145,000 square miles) of Loreto, which is a third of the total area.

Higher than normal floods occurred in Loreto in 2009, 2011, 2012, 2013, 2014 and 2015 during the high water season. Meanwhile droughts (lower water levels and less precipitation) occurred in 2005, 2010 and 2020 during the low water season.

It is thought that this intensification of the hydrological cycles will only increase in intensity in the future.

How does greater climactic fluctuation affect these flooded forests?

Flooded forest ecology revolves around the aquatic and terrestrial cycles. FundAmazonia has been surveying populations of terrestrial, arboreal and aquatic wildlife for the last 35 years, and the long-term data they have collected is being used to understand the impacts of the intensification of these hydrological cycles.

Some of their conclusions so far:

• Wildlife populations are sensitive to intensification during high floods and droughts.

• There have been shifts in populations of terrestrial, aquatic and arboreal animal species.

• Changes in fish and wildlife populations - which are important sources of meat for local people - are impacting their harvests and livelihoods.

The research is ongoing, and you can get involved with it by booking a minimum of three nights on the Rio Amazonas Research Station.