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Name:__________________________ Final Exam Physical Geography (Thoroughly explain!) 1. In Africa, which portion of the ecotone formed between the tropical deciduous biome and the Tropical savanna biome is growing, which way is it moving, and what are the causes? 5 pts 2. Why is clear cutting of rain and deciduous forests in the tropic regions a bad idea? 5 pts 3.

What effects does a warming world have on the Northern Hemisphere's Biomes? 5 pts Please explain this graph in the context of what we have discussed in class: 4. What was the cause of the warm up starting at ~18,000 and ~130,000 years ago? 5 pts 5. What was the cause of the initial plunge into the glacial phases after the interglacials?

5 pts 6. Today is the fifth time the world’s temperature has been above the “0†line on this graph. Why is CO2 also high at each of these times? Dust concentration in the atmosphere is high when CO2 and temperature is low. Why?

5 pts Extra credit: In this warming interglacial, what should be happening to estuaries? Why not? 3 pts

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Final Exam Physical Geography

1. The Ecotone Between Tropical Deciduous Biome and Tropical Savanna Biome in Africa

The ecotone that exists between the tropical deciduous forests and the tropical savanna biome in Africa is primarily growing in the region known as the Sudano-Sahelian zone. This ecotone is moving northwards, encroaching upon the areas traditionally dominated by the tropical savanna biome. Several factors are contributing to this shift, including climatic changes, increasing temperatures, and human activities such as deforestation and land conversion for agriculture.
As global temperatures rise due to climate change, the growing season for tropical deciduous forests tends to expand, allowing these species to migrate further into savanna regions (Scholes & Archer, 1997). Concurrently, increasing drought frequency in some areas leads to the dieback of savanna trees, facilitating forest encroachment (Foley et al., 2003). This movement is compounded by anthropogenic factors such as agriculture, where cultivation practices often favor the establishment and spread of deciduous species, altering the balance between these two biomes (Turner et al., 2015).

2. The Pitfalls of Clear-Cutting Tropical Rain and Deciduous Forests

Clear-cutting tropical rainforests and deciduous forests is detrimental for several reasons. Firstly, these forests play a critical role in carbon sequestration, helping to mitigate climate change by absorbing CO2 from the atmosphere. Removing these trees can release stored carbon, exacerbating global warming (Pan et al., 2011).
Secondly, clear-cutting disrupts local ecosystems and biodiversity, which can lead to the extinction of endemic species that rely on specific habitats found in these forests (Wright, 2005). Additionally, clearing vast areas of forest can cause soil erosion and degradation, reducing land productivity and leading to problems such as desertification (FAO, 2016).
Finally, clear-cutting has significant socio-economic implications for local communities that rely on forests for their livelihoods, leading to social unrest and economic hardship (Colfer et al., 2016). Therefore, sustainable forest management practices are essential to preserve biodiverse ecosystems and maintain the ecological balance.

3. Effects of a Warming World on Northern Hemisphere Biomes

A warming climate has profound implications for the biomes of the Northern Hemisphere. As temperatures increase, researchers observe shifts in species distributions, with many plants and animals migrating northward or to higher elevations as their optimal conditions change (Parmesan & Yohe, 2003).
In boreal forests, warmer temperatures can lead to increased growth rates for some tree species while leaving them vulnerable to pests and diseases that thrive in warmer climates (Lindner et al., 2010). Furthermore, the permafrost melting as a result of warming poses risks for ecosystems, releasing methane and CO2, which further exacerbates climate change (Gorham, 1991).
In tundra ecosystems, rising temperatures can result in changes to vegetation, with shrubs and woody plants increasingly encroaching into areas traditionally dominated by mosses and grasses (Myers-Smith et al., 2011). This shift can further alter carbon storage and local wildlife habitats, creating downstream effects on the entire ecosystem.

4. The Causes of Warm Up ~18,000 and ~130,000 Years Ago

The warm-up periods around 18,000 years ago and 130,000 years ago can be attributed primarily to changes in Earth's orbital configurations, known as Milankovitch cycles (Hays et al., 1976). These cycles describe the variations in Earth's axial tilt, precession, and eccentricity which lead to changes in solar radiation received by Earth, significantly influencing climate and glaciation patterns.
Specifically, the termination of glacial periods is marked by a rise in summer insolation, particularly in the Northern Hemisphere, which triggers the melting of massive ice sheets. This melting leads to a feedback loop where the release of fresh water into the oceans alters oceanic currents and further modifies global climate patterns (Ruddiman, 2003).

5. Initial Plunge into Glacial Phases After Interglacials

The plunge into glacial phases post-interglacials is largely influenced by the same Milankovitch cycles. A drop in solar insolation, particularly during summer months, results in cooler temperatures that promote snow accumulation over glacier regions (Ruddiman, 2003).
As these ice sheets expand, they reflect more sunlight (increased albedo), which leads to further cooling. Additionally, changes in oceanic circulations, which can result from shifts in salinity and temperature, often lead to decreased heat distribution and contribute to more stringent glacial conditions (Broecker, 1997).

6. CO2 Levels in Relation to Temperature Variations

During warm periods, CO2 concentrations are high due to a variety of natural processes such as increased respiration rates and decomposing organic matter release from warmed soils (Liu et al., 2016). In contrast, periods of low CO2 concentration, such as during glacial phases, are often associated with extensive dust accumulation because vegetation cover is diminished, leading to more exposed soil and increased wind erosion (Kohfeld & Harrison, 2001).
The link between lower temperatures and high dust concentrations is further clarified by the role of dust in cloud nucleation, where more dust can lead to increased cloud cover and cooler terrestrial temperatures (Kaufman et al., 2001). Thus, the relationship between CO2 and temperature is an intricate interplay of various biochemical and geological processes.

Extra Credit: Implications for Estuaries in a Warming Interglacial

In a warming interglacial phase, estuaries should be experiencing an increase in freshwater input from melting ice and altered precipitation patterns, potentially affecting salinity levels and nutrient dynamics (Wetzel, 2001). However, anthropogenic factors such as urbanization, industrial runoff, and pollution often counteract potential benefits, leading to degradation of these vital ecosystems (Burkholder et al., 2007). Consequently, effective management and restoration efforts are essential to enhance the resilience of estuarine systems in the face of rapid climate change.

References

1. Broecker, W. S. (1997). Thermohaline Circulation, the Achilles Heel of Our Climate System: The Greenhouse Effect. Science, 278(5337), 1586–1592.
2. Burkholder, J. M., et al. (2007). Eutrophication and Oligotrophication in Coastal Marine Ecosystems: A False Dichotomy. Journal of Coastal Research, 23(1), 56-80.
3. Colfer, C. J. P., et al. (2016). Does Tenure Matter? A Study of Forest Users’ Experiences and Their Contributions to Sustainable Forest Management. Environmental Science & Policy, 60, 45-53.
4. FAO. (2016). Global Forest Resources Assessment 2015: How Are the World’s Forests Changing? Food and Agriculture Organization of the United Nations.
5. Foley, J. A., et al. (2003). Global Consequences of Land use. Science, 309(5734), 570-574.
6. Gorham, E. (1991). Northern Peatlands: Role in the Carbon Cycle and Climatic Change. Wetlands Ecology and Management, 1, 99–113.
7. Hays, J. D., et al. (1976). Variations in the Earth's Orbit: Pacemaker of the Ice Ages. Science, 194(4270), 1121–1132.
8. Kaufman, Y. J., et al. (2001). Dust Transport and Climate: A Case Study in the Atmosphere. Journal of Climate, 14(19), 410-428.
9. Kohfeld, K. E. & Harrison, S. P. (2001). Paleo-Climate Controls on the Distribution of Glacial Dust. Geophysical Research Letters, 28(14), 2711-2714.
10. Lindner, M., et al. (2010). Climate Change Impacts in Forests: New Evidence in the context of European Biodiversity Indicators. Forest Ecology and Management, 259(4), 507-518.