I. Introduction

Solving Complex Problems grew out of concerns from the MIT faculty about the freshman year. The class was proposed as an experiment in freshman education by Professor Kip of the Earth and Planetary Sciences Department. Professor Hodges hypothesized that given complete control of their education, freshman would not only succeed, but flourish with enthusiasm. The first incarnation of the class, Mission 2004, challenged students to “develop a viable mission plan for the exploration of mars with the aim of finding evidence for the present or past existence of life.” For the second year students were challenged “to design permanent, manned, underwater research laboratories and to develop detailed research plans for the first six months of their operation.” Now in the third year of the experiment, the class of 2006 was challenged to “develop a way to characterize and monitor the well-being of one of the last true frontiers on Earth – the Amazon Basin rainforest – and devise a set of practical strategies to ensure its preservation.”

The water group grew out of the need to effectively complete this mission. The class felt it necessary to divide ourselves into nine groups, each composed of four to seven students. Each group was then charged with a specific responsibility to the greater mission. In particular, the water group’s goals have been to analyze the hydrologic cycle, monitor the chemical composition of the water, and examine the effects of human development in the Amazon Basin rainforest.

The purpose of this document is to summarize the water group’s findings on the Amazon Basin rainforest water system. Particular emphasis is placed on the hydrologic cycle, aquatic biota, sedimentology, and the effects on these processes by deforestation, pollution, hydroelectric power plant construction, and mining.

Hydrologic Cycle

Our approach to the hydrologic cycle has been to analyze the cycle in terms of the flux of water into and out of the system, as well as the evolution of water inside the system. This translates into studying precipitation, precipitation recycling – evaporation and evapotranspiration, and river flows. This approach has led us to identify two major trends in the hydrologic cycle. The first of these trends is decreasing atmospheric transport of water vapor both into and out of the system. This is believed to be associated with relaxed southeasterly trade winds, a decreasing east-to-west pressure gradient, and a general warming of the sea surface temperatures in the equatorial South Atlantic. The second trend we identified is increasing internal recycling of precipitation and basin-wide precipitation.

Aquatic Biota

Our approach here was to identify the effects on aquatic biota by human development, with particular emphasis on artificial water management. Under this research area we also explored the possibility of using parasites as a proxy for measuring water quality and pollutions levels.

Sedimentology

Our approach to sedimentology was similar to that of aquatic biota, identifying the effects of human development, an in particular damming on the transport of sediment.

Deforestation

From what we have read and learned, deforestation is the principle problem facing the water system of the Amazon Basin rainforest. Deforestation affects all abiotic and biotic systems, disturbing the natural equilibrium of the region. For example, one effect of deforestation on the hydrologic cycle is to deprive the soil of important nutrients, as rainfall easily washes away the nutrient-rich top soil. This is possible because deforestation removes the trees that secure the soil to the land. Deforestation also has the effect of decreasing evapotranspiration, precipitation, and total runoff.

Pollution

Another major threat to the health of the Amazon Basin rainforest water system is pollution and in particular, mercury. Gold mining, which releases mercury both into the atmosphere and into the rivers, is one of the major causes of excess mercury in the water system. At times, the rate of production of mercury equals that of gold. Excess mercury in the water system is also caused by the recent colonization of the drainage basins and the growing exploration of land in the central Amazon. These actions both disturb mineral and organic matter cycles, including that of mercury. This results in increased exportation of fine particulate matter from the soil surface to drainage waters. Consequently, bioaccumulation occurs, whereby animals in the Amazon Basin’s rivers slowly accumulate mercury in their bodies. Higher-order species of the food chain then accumulate mercy stores in their bodies by consuming lower-order species. It is easy to see then that humans will exhibit supernormal concentrations of mercury in their blood streams from eating contaminated fish.

Pollution

In addition to releasing mercury into the environment, mining releases nickel, chromium, copper, and arsenic. Acid mine drainage contains dissolved and particulate metals in toxic concentrations that affect the pH of streams and mobilize metals. Malaria is a secondary result from the fact that stagnant water often accumulates at mining sites. These pools easily become mosquito breeding ground.

Hydroelectric Power

A third major perturbation to the water system of Amazon Basin rainforest is the construction of dams. Hydroelectric Dams affect the river in the following detrimental ways: 1) Create water reservoirs/stagnant pools, 2) Increase water temperature, 3) Increase flooding, 4) Increase eutrophication, 5) Increase gas formation, 6) Decreased water oxygen content, 7) Increased siltation, and 8) Increased phosphorous and nitrogen content.

In summary, humans are reeking devastating effects on the health of the water system of the Amazon Basin rainforest. Estimates show that if deforestation continues at its present rate, the region will be completely deforested within the next century. Even if the rate of deforestation is slowed, some forecast that past a certain point, the rainforest will be unable to support itself, leading to self-destruction. Clearly, action must be taken now to reverse these trends in order to preserve the Amazon for future generations.

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