PBL ANSWER KEYS
(Answers will vary greatly; this is just a guide)
Biomass Burning Problem Statement:
Our task is to research and evaluate all factors that contribute to and subsequently the consequences of, biomass burning (tropical rain forest destruction) in S. America. We have identified regional and global impacts, which include changes in air, soil and water quality, as well as decreases in species, habitat, and cultural biodiversity. Our further analysis will focus on identifying the root causes of forest destruction. This will be followed by generating strategies to prevent further degradation, as well as methods for minimizing the consequences of damage already done.
Biomass Burning Hypothesis:
Tropical rain forests are extremely rich ecosystems with massive amounts of biomass. The incredible biodiversity in soil bacteria, fungi, and protists allows for a multilayered forest structure, which in turn provides habitat for an equally diverse collection of animals. Continued burning of these tropical forests will have a huge impact on the earth for a few key reasons. The first impact is of course the continued loss of species diversity, as many species become extinct without having ever been identified. This impact could carry untold significance, as ethnobotanist’s rush to assay for chemicals in these unidentified plants, which could hold promise as cures for modern diseases. A second impact would be the disruption in the global cycling of gases. A third subsequent impact then would be in the form of global climate change, and a fourth would be the continued loss of cultures, as the self-sustaining peoples who depend on the rain forest for their existence will become increasingly exposed to modern ways. It is for these reasons that we must generate a plan to slow the process of tropical deforestation.
Biomass Burning Earth System Science Interaction Analysis:
Event > Lithosphere > Biosphere:
The nutrient cycling in tropical forests is unique; in that most of the nutrients are kept not in the soil, but in the plant tissues themselves. Conditions are so conducive to plant growth that the availability of soil nutrients is the primary limiting growth factor. As nutrients are returned to the soil in the form of animal wastes, dead plants and other detritus, soil decomposing bacteria immediately release those nutrients back into the soil, where just as quickly, they are taken back out of the soil by plant roots, eagerly seeking nutrients. As deforestation occurs, a couple of things typically occur. Large hardwood trees, such as mahogany and teak, are removed for export to countries like the United States. The remaining trees and under plants are then typically burned to clear the forest for raising cattle or other agricultural purposes. The irony involved is that once the plant material has been removed, either physically or by burning, the soil holds so few nutrients that the land is very quickly rendered useless, unsuitable for raising cattle or growing crops. The next step then, of course, is to clear more forest…
Event > Atmosphere:
The massive amount of photosynthetic tissue present in tropical forests is a huge sink for carbon dioxide. Continued removal of trees and other plants will reduce the rate of photosynthesis, which will in turn result in a net increase in atmospheric carbon dioxide. The burning of the fallen forest materials would also subsequently release large quantities of carbon dioxide, along with a variety of other gases. With carbon dioxide being a greenhouse gas, there would then be a good chance that the global warming trend would worsen.
Atmosphere > Biosphere:
If increasing amounts of trace gases and aerosols cause more global warming, a wide variety of biological impacts could result. The most fundamental would be the forced migration (or extinction) of many species of life forms, as environmental conditions would move outside of the range of tolerance. Species would theoretically be forced to move toward the poles to keep their environmental conditions the same. Species unable to migrate successfully would ultimately go extinct.
Event > Biosphere:
As huge patches of forest are destroyed, hundreds of species of plant, animal, bacteria and fungi may be destroyed as well. The chemicals in those extinct organisms will also be forever lost. Native cultures in the forests have used a very diverse collection of plants to treat a full spectrum of medical conditions for a very long time. If the forests are destroyed before the knowledge and the cultures can be preserved, the medicines will be destroyed as well.