The future of the Amazon? A week in Manaus

August 22nd, 2006 by David
Universidade Nacional Amazones

   I spent a week in Manaus, staying in the apartment of two graduate students and visiting Instituto National de Pesquisas da Amazonia (INPA), a famous research center. Here, in addition to giving a presentation for INPA and also for students at a neighboring University, I talked with scientists modelling climate in the Amazon rainforest. From what I gather, the rainforest faces three major threats. 1) Direct deforestation, 2) Decreased rainfall caused by deforestation, and 3) the possibility that global warming will dry out the basin.

   Although the Amazon basin is enormous (similar in size to the contiguous U.S.), deforestation is a major threat. Everywhere roads are built, the forest is cut down, making way for fields of soy beans or beef cattle. From one of the researchers at INPA, I received the images below which show the forest in 1992, deforestation by 2002, and then projected deforestation in 2033 (deforestation shown in red).

Amazon 1992 - forest shown in green
Amazon 2002 - deforestation shown in red
Amazon projected 2033 - deforestation shown in red, source: Soares-Filho et al., 2004
Francis, Theo, and their supercomputer for climate modeling

   I talked with two climate modellers at INPA, Francis and Theotonio (shown on the right with their ‘supercomputer’), about how this deforestation would affect the rainforest, as cutting down a forest changes evaporation and thus rain patterns. If the entire forest were cut down, they estimate that rainfall would decrease on average 30%, with many areas becoming too dry for forest. Indeed, one study suggests that there are two stable states of the Amazon – one state like the rainforest we find today, and another state where much of the forest is dry savannah. If too much forest is cut down, there is a possibility that it would push much of the Amazon into the drier state, unable to easily return to forest. (More on this here.)

   These studies, however, do not consider the effects of global warming. To be sure, the effects of global warming are uncertain because large scale climate models are not good at modelling rainfall in the tropics. Nonetheless, a few models (not all) suggest that a warmer earth means a much drier Amazon, which would turn much of the basin into savannah. This may be wrong. It may also be correct.

   Decreasing rain and savannahization are real risks to the rainforest. Due to uncertainty in the science–we can’t be sure if deforestation or global warming will reduce rain–it is difficult to put percentages on these risks, and Theotonio and Francis, while claiming it a real possibility, balked at guessing its probability. Nonetheless, if it is true, the results are very bad. A loss of the Amazon would not only loose countless species, but also release incredible amounts of carbon dioxide to the atmosphere, accelerating global warming. Do we really want to find out if it is true or not?

Tower to measure carbon dioxide fluxes in the Amazon
Alex downloading data
Reminds me of an experiment I used to work on...
Nice forest - look at the diversity of trees!

   My last full day in Manaus, I travelled with Alexender, one of my hosts, to a large forest preserve near the city. In the preserve, Alex maintains a large tower that measures CO2 concentrations, and is he trying to understand how CO2 fluxes into and out of the forest. Alex let me climb to the top of the tower, where I was able to look across the treetops of a forest that stretches for thousands of miles beyond the horizon. Listening to the birds, monkeys, and insects, it was hard not to be both awed by the Amazon and to wonder what its future will be.

3 Responses to “The future of the Amazon? A week in Manaus”

  1. Daisy says:

    Wow, Dave! Your journey has taken you far. The questions you are asking are important ones for the future of the world. I’m amazed that you chose to take the route through Colombia and into the north of Brasil. As you go further south, it is very interesting how the climate and environs change, and how disconnected from the Amazon the people are. Eat some acai while you’re there!!

  2. yasna aguilar says:

    hopefully the people realize of wich this happening in the world, but to the people does not say to him what they must do are not going to do nothing, so that they do not realize of wich it happens in the world. This very well what these doing. Hopefully someday they find a solution to wich this happening around the world. Yasna.
    I am chilean, and I write in English by a translator.

  3. Suely Roussenq says:

    Parabens, muita coragem.

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