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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Without plants to hold soil moisture, surface runoff increases, wells dry, the microclimate becomes inhospitable for plants, and deserts occur.
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.
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 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.
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.
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.
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.
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.
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.
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.