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Land and Food Resources I. Potential Test Questions. What five ecosystem services are provided by natural areas. Discuss. 2. Discuss the ‘tragedy of the commons,’ the ways in which we have ‘commons’ in the United States, and solutions to the tragedy.
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Potential Test Questions • What five ecosystem services are provided by natural areas. Discuss. • 2. Discuss the ‘tragedy of the commons,’ the ways in which we have ‘commons’ in the United States, and solutions to the tragedy. • 3. How can overgrazing affect desertification. (Make sure to explain why grasslands can tolerate grazing, how overgrazing effects grasslands, and what desertification is).
Potential Test Questions • 4. Discuss tropical deforestation and its causes. Explain swidden agriculture in your discussion. • 5. What are the BLM and USFS? What policies have they had in place that are harmful to U.S. ecosystems. Explain.
Ecosystem Services of Natural Areas: • Wildlife habitat (protect species) • Flood and erosion control • Soil formation/maintenance • Groundwater recharge • Recycle wastes (nutrient cycles) and break down pollutants
Pasture and Open Rangeland • Predominantly grasses with a fibrous root system. Rangelands occupy about 26% of the world’s land surface.
Pasture and Open Rangeland • There is twice as much permanent grazing land as area given to agricultural crops in the world. Much of the western Great Plains and the Prairie provinces of Canada fall in this category.
Pasture and Open Rangeland: • Carefully managed, grazing can be sustained in grasslands (with the loss of a few grazing-intolerant plant species), because most species are tolerant of being grazed. • For the U.S., rangeland/prairies have more species of plants, and more threatened species of plants, than any other biome type.
Pasture and Open Rangeland: • Benefits of grazing include: • Hooves create seed-to-soil contact • Natural grazers break soil crusts that keep seeds from growing • Grazers trample standing vegetation into mulch • Grazers act like living compost piles, turning vegetation into high-quality fertilizer • By pruning stale growth, they keep forage plants at peak production
Pasture and Open Rangeland: • Effects of overgrazing grazing include: • Compacting soil thus preventing seeds from germinating and water from seeping into soil. • Overfeeding on plants not allowing them time to recover and adequately root.
Overgrazing • Overgrazing is when plants are consumed such that the plant community does not quickly recover. • 1/3rd of the world’s range is severely degraded by overgrazing, making it the largest cause of soil degradation.
Overgrazing • The first symptom of overgrazing is the loss of palatable species of herbs and grasses. Continued overgrazing compacts the soil, strips the ground bare, and leads to erosion.
Desertification • Continued degradation leads to a fertile land becoming more desert-like. Without plants to hold soil moisture, surface runoff increases, wells dry, the microclimate becomes inhospitable for plants, and deserts occur.
Desertification • In Africa, deserts have increased by 50 million hectares, and humid or semiarid lands have decreased by that amount. Is human activity responsible?
Remember the Tragedy of the Commons • Any commonly held resource becomes degraded or destroyed because the narrow self-interests of individuals tend to outweigh the public interests.
U.S. Rangelands • Bureau of Land Management (BLM): 200 million acres • U.S. Forest Service (USFS): 50 million acres • 60% of rangeland is privately owned. • 55% of public rangelands are in poor condition (sage, mesquite, cheatgrass, and cactus). • Grazing fees: grazing permits on BLM or USFS land was $1.35 per animal. It costs them $3.21 per animal to administer grazing. This equals a lossof of $32 million. • Few people hold most of these permits = welfare for rich cattlemen.
Forests and Forest Products The amount of fuel wood consumed by each person in developing countries is roughly equal to that used as paper products by each American. Demand for fuel wood will be twice the available supply in just 25 years.
The Rates of Deforestation Are Increasing • Consider Costa Rica, an environmental success story. Lost 75% of its primary forests in the last 60 years due to timber harvest, Del-Monte plantations, cattle grazing (mostly for export).
Costa Rica (the “Green Republic”) Costa Rica contains more biological diversity than all of North America combined. Costa Rica encompasses only.03% of the world’s landmass, but it contains and supports 5-6% of the entire world’s biodiversity.
Costa Rica Policies Costa Rican Government has been a front runner in conservation policy - 90% of its remaining forest is protected, and it has the largest percentage of land dedicated to national parks in the world. Emphasis has been on sustainability. Along with a strong conservation policy, the Costa Rican Government has enacted incentive programs to promote reforestation projects. These incentive programs include such things as residency status and various tax exemptions.
Causes of Tropical Rainforest Destruction • Commercial Logging:tropical forests harvested for timber. • Subsistence agriculture: “slash and burn tactics” (also called swidden or milpa agriculture). • Cattle ranching:After commercial harvesting or after subsistence agriculture, or on its own.
“Slash and Burn” (Swidden or Milpa Agriculture. Farmers clear a small plot (2 acres), burn the dried plants to provide a burst of nutrients (and ash is basic, increasing the release of minerals from clay). On field, they practice polyculture (using some perennials). Banana/plantain, papayas, cassava and sweet potato (root crops), beans (increase nitrogen), and maize (plots hold the soil because there is a variety of roots). In time, the plot is given over to encroaching forest because the fertility has decreased, and the farm begins in a new area.
Milpa Agriculture Depends on land to rotate through. If the farm remains long term, the productivity of the land declines. Higher populations are increasing the pressure on the land and not allowing enough time for recovery.
Cattle Ranching • Ranching often introduced after commercial harvesting or after subsistence agriculture, or on its own. Tropical soils are Oxisols and ultisols - soils that are highly leached and nutrient poor. Minerals are locked up in the vegetation; if vegetation is lost, minerals are lost. So, it is hard to go from a pasture back to a forest again.
Logging in the U.S.A. Kinds of cutting: Clear cutting:removal of all wood in a compartment. Strip cutting:harvesting strips within a compartment on a rotational basis. Selective cutting:planned removal of individual trees or small groups of trees within a forest stand.
Cost effective because large machines can be used, making it easier to fell, trim and skid logs. • But: 1. Eliminates almost all habitat • 2. Increases soil erosion greatly • 3. Favors early succession tree species and deer (game) • 4. Increases soil and water temperatures. • Sometimes seed trees or nurse plants left Clear Cutting:
Strip Cutting 1. Reduces erosion compared to clear cutting 2. Provides seed sources for establishment, But strip cutting still favors early successional tree species and edge animals.
Selective Cutting • Favors the more shade-tolerant trees like red spruce, sugar maple and hemlock because the shade is not broken. • 2. Provides a continuing supply of food and cover for wildlife throughout the life of the forest. • 3. An uneven-aged stand is particularly favorable to birds.
Selective Cutting Need intensive skilled management to prevent degradation of the remaining stand (genetically superior trees are likely to be removed). Management and skidding costs are likely to be higher, road construction and maintenance must be more extensive. High grading - taking out the few choice trees for profit and leaving the rest. Lowest impact, but requires other skidding techniques.
