After 10 years of trying, Hays finally spots a "Red Eyed Tree Frog" in Costa Rica
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While intense emphasis and coverage of this hot topic has slightly decreased, deforestation is a huge problem that the world faces in the near future. The three areas of highest concern in the world today are Asia, Africa and the Americas--where the tropics experience the highest pace of conversion at 10 million ha/year (Laurance, 1999). Deforestation is a non-random, unnatural process thus, not all forest types are equally endangered. The most vulnerable are accessible areas with relatively productive, well-drained soils and moderate topography--which are also most suitable for farming. Deforestation is the cutting, clearing, and removal of rainforest or related ecosystems, and subsequent conversion into other, less biodiverse, anthropogenic ecosystems such as pasture, cropland, or plantation (Kricher 1997).
Costa Rica has been a “poster child” for preservation of its resources. Currently Costa Rica has over 8,000 species of plants, but it has also lost over 60% of its forest cover. In 1970, as the cost of oil rose and the demand for coffee dropped, cattle ranching became a favored source of income, leading to the mass deforestation that Costa Rica has experienced. By 1977 all major regions of the country had been covered by roads and only high mountain forests were left undisturbed (Sader and Joyce, 1988). Since then, Costa Rica's efforts to save all it has left serves as an excellent example for other countries experiencing the same type of economic difficulties. Costa Rica has converted large amounts of its land into national parks. However, while nature reserves and parks are essential for sustaining current biodiversity, they are inadequate in assuring maintenance of existing environments of tropical forests (Putz et al., 2001). Costa Rica is still undergoing heavy deforestation. In 1998 Costa Rica’s tropical forests were experiencing logging intensities of approximately 50 to 100 m3/ha (Putz et al., 2001). Logging (just one form of deforestation) is a problem, however, the greater ecological problems are the consequences of it, such as fragmentation, overall greater access to the forests, vulnerability to forest fires, increased hunting, land conversion, etc. It is important for all of us, as habitants of this earth to be aware of the causes and different means of deforestation, its long-term consequnces, and the economic implications. We must learn of and implement ecologically-friendlier forms of deforestation and economic alternatives.
Causes of deforestation
There are many different hypotheses behind what drives deforestation. While to many there seems to be a simple answer--high population growth--the real reasons behind it are much more complex. Geist and Lambin 2002 have identified and researched several reasons such as national policies which promote land use, the technological drive for mass production that exists in our world today, the economic drive for agricultural and wood production, the necessity for cattle pasture land creation and development which leads to road construction providing access to remote areas for natural resources, for attracting tourists, increasing colonization and much more. As the human population increases, so does poverty. As poverty increases, the governments do everything possible to stabilize their economies and bring income into their countries. The growing population of people need a place to live, thus they move out of the city and into rural areas, where trees are cut down to make room for homes, farms. Geist and Lambin 2002 have found that agricultural expansion is the leading form of land-use associated with deforestation (96%). The greatest of all reasons is pasture creation for cattle ranching because it is an excellent form of income. However, the nutrients of the land are quickly depleted and thus new rainforest land must be cleared to create new lands for grazing. It is important to note that nutrient-depleted pastures take many years to become restored to their prior state. In order to keep the economy going the governments have lowered the costs of land, labor, fuel or timber, thus many foreign companies invest in these areas. Since there is little or no government regulation of ecological factors such as pollution, it makes for an attractive investment. Another driver of deforestation is the mismanagement of land tenure agreements. For example, not only is wood extraction not controlled, often times other issues arise, such as that of road construction, which only leads to further forest fragmentation and deforestation. Often times policies are pro-deforestation in order to boost the economy with the state offering low taxes, legal land titling, credit and other incentives which leads to further road construction, extensions of pastures, etc. Increasing trade liberalization and international free-trade agreements are also promoting greater foreign investment, further promoting deforestation (Laurance, 1999). Other causes of deforestation include hydropower development, mining, oil and gas exploration, commercial hunting (which endangers many species with low reproductive rates) and more.
Methods of deforestation
There are many forms of deforestation. The two most common are slash-and-burn and logging. In the slash-and-burn method the vegetation is first cut and then burned in order to release the minerals into the soil. The slash-and-burn method of deforestation leads to small pools of soil nitrogen. However, these pools are quickly depleted. Slash burning shows a dramatic short term increase in inorganic nitrogen and surface soil pH levels. A study done by Ellingston et al. found that net nitrification and overall mineralization rates were lower (immediately after burning, nitrogen mineralization was higher than in undisturbed plots, but this increase was short term). The reason why the increase of nitrogen is short term is because many of the nutrients are washed away by rain. There is no vegetation which keeps the nutrients in the soil. In the slash-and-burn method high rates of soil erosion are common and the vegetation structure is altered. All of this leads to difficulties in overcoming these barriers during restoration, reforestation or alternative land uses (Ellingston et al., 2000). Another danger is that once burned forests become increasingly prone to subsequent fires.
When properly planned and conducted logging can be an important component of forest management systems and promote sustained timber yields, unfortunately this is never the case (Putz et al., 2001). Logging is one of the most damaging and most financially lucrative practices. There are many silvicultural interventions designed to increase stocking of commercial tree species or increase the growth of trees already present, but logging, because most often it is done in a wasteful manner, is one of the most severe (Putz et al., 2001). Intensities of logging vary over time, however, it alters the composition of the landscape, thus influencing its inhabitants. Trees are not only cut down (much of which is done illegally), mortality rates of nearby damaged trees increase. Another method of logging is clear-cut logging where all the trees are cut and the ground is left bare, no tree trunks, no nutrients. Thus, no one knows how long such an area will take to grow back, scientists guestimate that it will be about 50 years or so. Logging affects nutrient and hydraulic cycles and changes biogeochemical stocks (Putz et al., 2001). It leads to networks of roads, which is unnecessary tree mortality. This fragmentation makes the forest more vulnerable to forest fires, especially during droughts, which only increases deforestation levels. Logging leads to soil erosion and compaction. Grasses and vines invade the cleared areas. Clear lands experience soil fertility declines and then require many fallow years for nutrient recovery. Thus if new areas are not permitted to be cut, farmers will have to use quite heavy, expensive fertilizers, further upsetting the nitrogen cycle.
Much of forest clearance in Costa Rica was for cattle ranchers (Park 1992). Nearly 2/3 of Costa Rica’s rainforest has been destroyed for cattle ranching. However what few realized before it was too late is that rainforest soil is not suitable for animal grazing or crop production because it quickly loses its fertility. Cattle grazing destroys the physical and chemical structure of the soil in just a few years. Land is cheap because government promotes farming, thus nutrient-exhausted farms are left behind and the deforestation process is started elsewhere (Park 1992).
Long term consequences
We are experiencing three major global changes: increasing levels of carbon dioxide in the atmosphere, an increase in land use/land cover change and alteration in the biogeochemistry of the nitrogen cycle (Vitousek, 1994). These three have resulted and will lead to even more increased changes in climate and loss of biodiversity. Recently, we have undergone a sky-rocketing increase in atmospheric gases. These greenhouse gases have changed our climate by increasing surface temperatures, decreasing precipitation, decreasing humidity and changing atmospheric cycles. Zhang, et al. 2001 found that greenhouse gas warmed climate will lead to an increase in temperatures in the middle latitudes of northern and southern hemispheres. This may also lead to changes in large-scale atmospheric circulation, but it is not yet known what these changes will be.
Deforestation causes excess carbon to be released into the atmosphere, which increases global warming. It is important to note that an increase in CO2 levels is a result of fossil fuel combustion and not deforestation. However, deforestation has reduced the area and thus the effects of important carbon sinks, such as the Amazon basin. Plants also respond to increased carbon dioxide levels, but in various ways. Some plants increase their growth rate, however, the tissue they produce has lower nutrient concentrations, thus higher quantities must be consumed by herbivores to acquire sufficient levels of protein. Also increased levels of CO2 in seawater reduce over-saturation of aragonite -- a building block of coral reefs (Vitousek, 1994), which may lead to reduction in coral reef growth, but actual effects are not yet known. It is important to note that undisturbed forests are a globally significant carbon sink. New forests are only temporary carbon sinks because they have lost so much carbon initially via deforestation. The newly cut rainforests will only turn into sources of greenhouse gases (Laurance, 1999).
Recently we have experienced increased levels of nitrogen. By clearing land and burning forests humans have extracted nitrogen from long-term storage pools and released it into the atmosphere. This same rate of N fixation has also been noticed in an increase of atmospheric concentrations of nitrous oxide--another greenhouse gas (Vitousek, 1994). Enhanced nitrogen deposition has been noticed to cause forest dieback in European forests. The addition of nitrogen in the form of fertilizer, often used by farmers seems to increase primary production and biomass however it seems to decrease species richness. Increased levels of nitrogen in plant tissues seem to favor consumers, the opposite of the effects of CO2. An experiment testing the slash-and-burn method on nitrogen levels found a short-term increase in inorganic nitrogen and soil pH and high levels of erosion of burned areas (Ellingson et al., 1999). However, the potential rates of N mineralization were short-lived, and were significantly lower than those found in undisturbed rainforests. N and CO2 are not the only cycles experiencing a disruption or an increase. There are many other, including sulfur, whose change in cycle has led to sulfuric acid rain.
An increase in land use has had a significant change on land cover. Land cover change is the alteration of the physical or biotic nature of a site, such as the conversion of a rainforest to pasture land, while land use change involves alteration of the way humans use land, such as the conversion of low-input agricultural land to high-input uses (Vitousek, 1994). There is no global measure of land use change, nor is there any direct measure of deforestation. Land use change is one of the leading causes of increase in atmospheric concentrations of greenhouse gases. The slash-and burn method of deforestation has added high levels of nitric oxide, methane and carbon monoxide to the atmosphere. Locally this has led to increased temperatures and decreased humidity--characteristics of dryer climates--which may lead to susceptibility to fires and affect the rate of forest regeneration. A simulation model done by Lean and Warrilow, 1989, shows that if the entire Amazonian forest was converted to pastures, the area would experience increase in temperature, decrease in precipitation and alter the patterns of atmospheric circulation.
Deforestation leads to greenhouse warming of climate. Changes in tropical rainforest regions lead to large reductions in surface evaporative transpiration (the process where water evaporates from within the leaves of plants) and precipitation. Reduced evaporative transpiration from large-scale deforestation could cause a 20% decline in rainfall, thus leading to a lower humidity, higher surface temperature and more severe dry-seasons (Laurance, 1998). This in turn may lead to the rainforests being replaced by drought-adapted deciduous forests or woodlands. An increase in surface temperature is not solely led by increases of CO2, but also by reduction of surface evaporative transpiration and atmospheric long-wave radiation (Zhang et al., 2001). Reduction in surface evaporative transpiration leads to lower relative humidity which leads to higher surface albedo. Surface albedo is the reflection of short-wave radiation. When surface albedo is increased, more short-wave radiation is absorbed at the surface and thus a lower amount of energy is put into the ecosystem. At the same time, long-wave radiation is increased towards the surface and out to space. These radiation fluxes affect the surface moisture levels and thermal properties. The atmosphere increases its’ ability to absorb long-wave radiation while short-wave radiation is let through, leading to trapped heat in the atmosphere. Deforestation leads to reduction of evaporative transpiration which leads to reduction of cloud cover. Reduction of cloud cover allows more radiation to reach the surface and reduces the effect of the increased surface albedo. Thus a smaller fraction of short-wave radiation is reflected. It also changes the long-wave radiation between the land-surface and the atmosphere allowing more long-wave radiation to escape. This loss of surface latent heat of outgoing long-wave radiation is offset by further reduction of cloud cover in order to maintain the increased surface temperature. Thus this vicious cycle continues becoming worse each time. Tropical forests are more sensitive to soil water availability. Areas where dry seasons are very prominent will be in danger. These areas survive now because they have deep root systems which allows them to overcome droughts. However, reduction in soil water availability of an already threatened species may be quite detrimental (Laurance, 1998).
Solutions/Alternatives
Conservation may be achieved through collaboration between loggers and environmentalists. For example the Debt-for-Nature-Swap program of 1987 (where the debt-ridden tropical countries trade areas of the forest for their international debt-- the country’s creditors sell the debt at a discount price to a conservation group or a foreign government) was quite successful in saving forest lands (Park 1992). A great source of income is ecotourism which brings in more money than wood exports in Costa Rica. Another idea is well managed logging which can mimic natural disturbances and if hunting is kept to a minimum, populations will avoid bottlenecks (Laurance, 1999). Sustainable forestry--where poor soils are used productively and no forest resource is over-exploited for a short-term gain (Park 1992) and sustainable agriculture are also wonderful options--such as changing from beef to dairy cattle in Costa Rica (Miller and Tangley 1991). Forest reserves such as La Amistad Biosphere Reserve, Costa Rica may not be equivalent to a natural untouched rainforest, but they are wonderful in preserving biodiversity (Miller and Tangley 1991). Another idea is growing forest from habitat fragments, for example the Guanacaste National Park, Costa Rica (Miller and Tangley 1991). The park is a dry forest that has been damaged by deforestation, however it has been restored through the efforts of the community which was educated about the benefits of a healthy living area. If more communities could be educated and convinced of the value of the rainforests, more people could be included in the restoration efforts and the deleterious effects could be minimized.
Why should we care?
The most important change of deforestation is the loss of biodiversity. Biodiversity, as defined by Putz et al., 2001 is the natural variety and variability among living organisms, the ecological complexes in which they naturally occur, and the ways in which they interact with each other and with the physical environment. The loss of species is permanent, while the level of biodiversity may be re-established after several billions of years, the combinations of genes will be lost forever. Tropical forests are not just incredible resources of biodiversity, they are homes to indigenous people who are the only ones who know the uses of many of the plants. Tropical forests are great supporters of the ecosystem they are a part of such as flood amelioration and soil conservation, they are crucial for maintaining stability of rivers and watersheds, they prevent soil erosion and much more. They are the most ancient, diverse and ecologically complex places on earth (Laurance, 1999), thus the irreversible loss of such treasures would be unforgivable and we must not let it happen.
Massive deforestation leads to severe weather patterns and climate changes. It is possible that further deforestation may lead to far more frequent El Ni–o events, such as the droughts of 1982-1983 and 1997-1998 and make them more severe, turn them into major catastrophes (Laurance, 1998).
Conclusions & our goals:
We should try to contribute to a better understanding of forestry and the effects on biodiversity of different activities. Much more research should be conducted, especially in the area of restoration and ways of counteracting the effects of forestry activities on biodiversity (Putz et al., 2001). Better logging practices could be implemented. Areas may be set aside within logging areas as reserves, which could act as buffer zones to the negative effects. The public of developing countries should become better educated about their governments' policies, about what they can do to change things and exactly how deforestation is affecting the world at large. Issues of population growth should also be addressed through out the world. Better proactive land-use strategies should be devised and funding of environmentally damaging projects should be discouraged (Laurance, 1999).
It is important to realize that all significant interventions in natural forests will have an effect on biodiversity (Putz et al., 2001). However, as practices improve, the negative environmental effects may be reduced. As the world population continues to increase and the earth's capacity for its' inhabitants continues to decrease, it is crucial that we take responsibility for our actions and their effect on our environment. Deforestation is and will remain to be a major concern for the centuries to come, not because we are in search of ascetically pleasing nature reserves but because it's affects play a crucial role in our ability to exist on earth.
Works Cited:
Ellingson, L.J., Kauffman, J.B., Cummings, D.L., Sanford, R.L., Jaramillo, V.J., 2000. Soil N dynamics associated with deforestation, biomass burning, and pasture conversion in a Mexican tropical dry forest. Forest Ecology and Management 137: 41-51.
Geist, H., and Lambin, E., 2002. Proximate Causes and Underlying Driving Forces of Tropical Deforestation. BioScience 52: 143-150.
Gradwohl, Judith and Russell Greenberg. Saving the Tropical Forests. London: Earthscan Publications, 1988.
Kricher, John. A Neotropical Companion: An Introduction to the Animals, Plants, & Ecosystems of the New World Tropics. Princeton, NJ: Princeton UP, 1997.
Laurance, William F. A Crisis in the Making: Responses of Amazonian Forests to Land Use and Climate Change. Tree 13: 411-415.
Laurance, William F. Reflections on the Tropical Deforestation Crisis. Biological Conservation 91: 109-117.
Miller, Kenton and Laura Tangley. Trees of Life: Saving Tropical Forests and their Biological Wealth. Boston, MA: Beacon, 1991.
Park, Chris C. Tropical Rainforests. London: Routledge, 1992.
Putz, Francis, 2001. Tropical Forest Management and Conservation of Biodiversity: an Overview. Conservation Biology 15: 7-20.
Sader, S. A. and Joyce, A. T., 1988. Deforestation Rates and Trends in Costa Rica 1940 to 1983. Biotropica. 20: 11-19.
Vitousek, Peter M. Beyond Global Warming: Ecology and Global Change. Ecology 75: 1861-1876.
Zhang, H., Henderson-Sellers, A., and McGuffie K., 2001. The Compounding Effects of Tropical Deforestation and Greenhouse Warming on Climate. Climatic Change 49: 309-338.
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