Presentation on theme: "Deforestation We Wish to Learn: What is “deforestation”? How have old growth forests been affected by humans? What are the consequences of loss of."— Presentation transcript:
Deforestation We Wish to Learn: What is “deforestation”? How have old growth forests been affected by humans? What are the consequences of loss of forest habitats and ecosystems? What management strategies are in place to preserve and restore forests?
Area of Forest Ecosystems World total: ~ 34 million km 2
Definitions Deforestation: The conversion of forest to another land use or the long-term reduction of the tree canopy cover below a 10 percent threshold. Deforestation implies the long-term or permanent loss of forest cover and its transformation into another land use. Primary forest: is a forest that has never been logged and has developed following natural disturbances and under natural processes, regardless of its age. Secondary forests: are forests regenerating largely through natural processes after significant human or natural disturbance, and which differ from primary forests in forest composition and/or canopy structure. Disturbed forests: Any forest type that has in its interior significant areas of disturbance by people, including clearing, felling for wood extraction, anthropogenic fires, road construction, etc. Frontier forests: large, ecologically intact, and relatively undisturbed forests that support the natural range of species and forest functions (WRI definition). Forest plantation is one established by planting or/and seeding in the process of afforestation or reforestation. It consists of introduced species or, in some cases, indigenous species.
Frontier Forests of the World Frontier forests 8,000 years ago Frontier forests Today Current non-frontier forests
Deforestation - A Global Pattern
Old-growth forests in the United States and Canada: Since 1600, 90% of the virgin forests that once covered much of the lower 48 states have been cleared away. Most of the remaining old-growth forests in the lower 48 states and Alaska are on public lands. In the Pacific Northwest about 80% of this forestland is slated for logging. Source: Wilderness Society, U.S. Forest Service, and Atlas Historique du Canada Virgin Forests 1600Virgin Forests 1993
Note regrowth since 1920s, of second- growth forest (Iverson 1991) Forest Area Change in Illinois Million Acres 1820: : : : : : 4.33
Note similarity of present deforestation rates in the tropics and past deforestation rates in Illinois. (Iverson et al. 1991) Deforestation Rates
Worldwide Distribution of Tropical Forests Tropical evergreen forest once covered ~ 16 million km2; today they cover about half their original extent.
Amazonia Brazil contains about 3.5 million km 2 of tropical forest, ~30% of the world's total. Almost all of Brazil's standing tropical forests are in the Amazon Basin, ~50% of Amazonia comprises upland areas: tropical rain forest. Perhaps another 0.5 million km 2 consist of transitional forests. In addition, there are large areas of savanna in the southern reaches of Amazonia.
Images of Amazonia Sloth in tree Macaw with Brazil nut See the GC1 lecture (www.globalchange.umich.edu/globalchange1/)
Satellite image analysis reveals increasing rates of deforestation in Amazonia, and transformation of forest land into agriculture and pasture
Brazil in the News REUTERS, Feb 3, 1998: Brasilia, Brazil — Brazil has created seven new national forests in the Amazon to foster sustainable logging and slow the destruction of rain forests. A decree signed by President Fernando Henrique Cardoso turns a total of 6.67 million acres of public land into areas which the Brazilian government may lease to loggers, the government's Environmental Institute (IBAMA) said in a statement. “With the decree … the government hopes to discourage the purchase of private land in the Amazon and at the same time encourage state governments to create their own networks of public forests” WASHINGTON POST, Feb 23, 1998 Statistics released this year show that in 1995 destruction of the Amazonian rain forest reached an all-time high. Just five years before, in 1990, some 11,000 square kilometers of forest were cleared in the Amazon. By 1995 that figure had almost tripled, to more than 29,000 square kilometers -- equivalent to 6 1/2 million football fields. Rondonia from Space, 1992
Forest Functions Source of wood products, including fuelwood (83% of all wood), building and non-wood products Influence climate conditions, affecting rainfall patterns and temperature Store nutrients and influence soil fertility Store carbon and act as potential CO2 “sink” Support natural ecological systems and helps to protect life diversity Provide recreational benefits
Wood and Non-Wood Products roundwood - wood in its natural state. May be used for building or processed into lumber, pulp, panels, paper & plywood food: nuts and fruits bark, dyes, fibers, gums, incense, latexes, oils, resins, shellac, tanning compounds & waxes Brazil nut harvesters (Castañeros) harvest the mature fruits after they fall to the forest floor
Forest Ecosystem Services protect watersheds and ensure perennial supplies of fresh water reduce sedimentation by mitigating erosion due to winds and surface run off prevent floods improve air quality enrich soil through plant litter and nitrogen fixation protect biodiversity Photo of muddy flood waters
Trees provide shade and their root systems hold soil
Endangered Species In June 1990, the Northern Spotted Owl was listed as an threatened species Lives in old-growth coniferous forests at the top of the food chain (needs to range widely) Logging in the Pacific Northwest takes place on public as well as private lands U.S. Forest Service and other federal agencies are caught between their traditional role, which includes permitting forest harvest, and growing desire to protect species and wildlands The Numbat - a marsupial lives off insects that inhabit decaying trees in old-growth forests
Causes of Deforestation Growing economies and consumption Population growth and demand for new land Bad economic policies Short-sighted political decisions Corruption and illegal trade Poverty and landlessness
Tropical hardwoods are highly valuable - ebony, teak, rosewood, etc. Their sale earns dollars for exporting countries, and enriches timber barons.
Economics of Timber Harvest Due to the slow renewal of a forest, and the high value of timber, it may be more profitable to sell the timber and invest the money, than to harvest the forest sustainably Due to political corruption, economic inequity and the powerless position of the poor, wealthy elites are able to pursue their short-term gain Long-range policies and environmental concerns often lack support among the wealthy and the poor When regulatory policies exist, they may rarely be enforced
Landlessness and Population Growth Many tropical countries with extensive forest are experiencing substantial population growth and urban migration. Historical discrepancies between wealthy landowners and poor peasants are reflected in political power structure, and so no land is available to give poor people work in the countryside Opening of forests to the landless poor is a social safety valve, reducing urban migration and conflicts between rich and poor.
Roads and Their Consequences Network of roads built into forests is extensive. One square km can have 20 km of roads In the U.S. forest system, there are 600,000 km of roads, built to facilitate timber harvest Road networks have serious consequences As forests are opened up, they become drier and more susceptible to fires. Fires in tropical forests were very rare. In 1997 severe fires raged in Brazil and Indonesia (remember the smoke problems in Indonesia) Bushmeat harvest enabled by road networks is depleting tropical forests of their wildlife
Forest fragmentation by roads in Central Africa. This study shows that 42% of forest area in the six countries is within 10 km of a road and more than 90% is within 50 km of a road. WRI Earthtrends
Forest Management and Recovery Forest management may have many goals - to maximize harvest, to provide recreational opportunities, or to maximize multiple uses of the forest Forest restoration may seek to restore the system to a near-natural or completely natural state, or to restore many aspects of the structure and function of an undisturbed forest
Some U.S. Forest Management Issues 2000 was the biggest wildfire year since the 1950s and advent of Smokey the bear. Today we have 50 years of wildfire suppression, coupled with the spread of humans into wildland interfaces. Iverson, L.R Biological trends in the United States: an annotated on- line review. Trends in wildlife area burned in wildfire in U.S.
Fire suppression plays a role in the impending “maple takeover” and “oak bottleneck” in the East. Oaks and hickory dominate the overstory, but maples will eventually take over, unless management actions can help regenerate oaks. Fire and Thinning to Restore Oak Communities
Prescribed burns help to kill maple saplings and may benefit oak regeneration. However, a more open canopy also is needed. Prescribed Fires
Thinning plus fire may help to recover oak forests Thinning
Timescales for Recovery uncut forest cut or burn farmed 2-3 yrs) 2 yrs pioneers emerge 15 yrs primaries emerge 100+ yrs to resemble uncut forest Time scales are such that it takes 100’s of years for a forest to regenerate If biomass is bulldozed away the forest may never regenerate If small plots of forests are cut, burned, farmed for a few years and then allowed to lie fallow, forest structure and biodiversity may persist
Scientists and others are experimenting with tropical forest restoration in many locations. Based on scientific understanding of forest dynamics, including light gaps, seed dispersal, and recruitment dynamics Even in very degraded areas, fragments of intact systems can be found in margins of altered areas Timescale of recovery is uncertain - no observational record of a full recovery to “old growth” conditions Tree nursery and planting seedlings, Restoration Ecology - natural recovery vs a “helping hand”
Forest Stewardship in Developing Countries Manage for long-term benefits Create economic opportunities for all parties Develop a balanced land-use plan based on sound science Have clear role for government and enforced regulations Involve all local stakeholders Conserve special areas
Tropical Forest “Hot Spots” Source: Norman Myers and Conservation International These 17 areas, believed to be unusually rich storehouses of biodiversity, are being deforested rapidly.
Summary Forest ecosystems provide valuable human products and ecosystem services Deforestation has already removed about half of the world’s forests, and in your lifetime threatens to eliminate most of the remaining tropical forests. Many temperate forests are re-growing, however Forests are managed for multiple uses, to restore as much of possible of natural ecosystem function, and in some cases to attempt to restore “old- growth” or pre-disturbance conditions