ENVIRONMENTAL ASPECTS OR SOCIO-ECONOMIC CONCERN

POTENTIAL IMPACT

Slopes

May become unstable, prone to slipping, sliding or earthflows; may become more vulnerable to earth quakes.

Banks and Shores

May become unstable and prong to undercutting or to long-chore erosion and deposition.

Soils

May be lost through rill, gully or shoot erosion, may become prong to rapid leaching of nutrients; may have rapid initial lose of organic matter, follow d by stabilization as soil organisms responsible for decay decrease in numbers; may become indurated as a result of laterization; micro-flora bad fauna may decrease or may be altered through exposure to full sunlight; in turn, changes in micro-organismic life may detrimentally affect decomposition and nutrient transfer; disappearance of mycorrhizae may, in particular, retard or prevent the re-establishment of the many tree species that feed symbiotically with these soil fungi; organic matter may increase under forest plantations, with beneficial effects on soil structure, infiltration capacity, soil-moisture holding capacity and cation-exchange capacity; accumulation of forest litter under plantations may also increase the danger of fire. Plantations of certain species may, on the other hand, detrimentally affect certain biophysical aspects of the soil (cf. Vegetation). Soil structure, organic content and micro-organisms may be affected negatively by fire used to clear forests for farming.

Sedimentation

Sediment load in streams mad increase with adverse effects on channel stability, navigation, fish spawning, bottom organisms (benthos), light penetration and other aspects of aquatic life, accelerated sedimentation may shorten the useful lifespan of reservoirs; on sloping ground, sediment from logged over areas may bury the roots of adjacent uncut forest or the crops on nearby fields; re- and afforestation may decrease sediment loads and thus reverse the negative effects described above.

Water Resources

Denuded slopes, compacted soils and decreased infiltration and canopy interception may lead to larger volumes of storm runoff and to quicker responses of runoff to precipitation; despite lower infiltration of rainfall, baseflow may increase locally after de forestation owing to decreased transpiration; however, large-scale deforestation usually results in lower down-basin low flows because of decreased infiltration and groundwater recharge, greater storm runoff and increased evaporation; smaller discharges may interfere with down-stream withdrawals for agriculture and domestic use. These effects may be reversed with re- or afforestation.

Reforestation in semi arid regions may, however, locally deplete soil moisture, lower water tables and result in decreased goundwater recharge and baseflow; this negative effect may be in part off set by increased infiltration capacity of soils under forest.

In humid areas, logging may indirectly raise water tables locally as transpiration is decreased; the use of heavy machinery may also cause local ponding of water, which in turn can drown seedlings and otherwise injure plants. Logging, floating of logs and improper disposal of slash and other organic debris may increase the turbidity and phenolic content of surface waters, and may accelerate the eutrophication of these waters through soil-nutrient losses and BOD loading of streams with debris; improper storage and disposal of fuel, lubricants, wood preservatives and biocides may contaminate surface and ground water.

Return water from irrigated tree plantations in semi arid areas may be saline; excessive fertilization of plantations may accelerate the eutrophication of waters.

Climate and Air Quality

Logging may increase ground temperatures and lower atmospheric humidity locally which, in turn, may interfere with seedling growth and micro-organismic life in the soil; large-scale deforestation may cause regional desiccation of the climate as transpiration is decreased, and local convection patterns are altered by changes in surface roughness and albedo; changes in the balance between sensible and latent heat (Bowen ratio) may, cumulatively affect global circulation patterns.

Logging in semi-arid regions or seasonally dry regions may release dust into the air; bare soils may become prone to wind deflation; tree felling, log hauling and other uses of machinery may release fumes; saw-milling, charcoal making and other wood transformation may cause local particulate and other emissions; large-scale deforestation may, cumulatively affect the global CO₂ balance, as tropical forests represent massive CO₂ fixation; although the recent increase in atmospheric CO₂ does not seem to be related to deforestation, there is need for caution before under taking massive consumption (burning, decay) of tropical wood. Deforestation has apparently a negligible effect on the global O₂ balance, presumably so long as the total surface of land vegetation remains essentially unchanged.

Vegetation

Moist tropical high forest may not regenerate itself at all after clear-cutting. Clear-cutting may eliminate entire endemic species or substantial portions of the total gene pool of certain species, including timber species. Total forest removal in areas of high species diversity increases the likelihood of loss of species and of genetic resources. On the other hand, clear-cutting and replacement of the natural forest with highly productive plantations can mean that fewer inroads are made into natural forests elsewhere. Selective logging of superior trees men cause genetic erosion. It may also damage much of the residual vegetation; seed trees may not survive because of "isolation shock" or because of mechanical damage during logging. Simplification of the forest through selective cutting or enrichment plantings with few species may reduce the overall resilience of the forest to pests and pathogens. On the other hand, the removal of over-mature, mature and defective trees may "release" other trees, there by increasing the health and productivity of the forest. Defective trees, such as hollow trees, may, however, be ecologically valuable (cf. Wildlife). Logging may, indirectly make adjacent uncut forests more vulnerable to windthrow, fire, illegal felling and shifting cultivation; alteration of the local hydrology and root burial by sediment may also affect adjacent vegetation adversely. Adjacent or residual stands can suffer mechanical damage during logging. The use of arboricides and other biocides may interfere with seedling growth, damage crops and adversely affect animal life, including human reproduction. Deforestation (land clearance for agriculture) by means of fire (or in areas unsuited for this technique) can damage residual vegetation, as well as soils, wildlife and fisheries. Plantations of certain species may detrimentally change the pH, specific nutrient status and micro-organismic life of soils, while improving organic content, structure and cation-exchange capacity of soils. Plantations of conifers may be especially prone to forest fires; they may require fire roads (10-12 m wide) and fire strips. Forest removal and replacement with exotics may deprive some animal species of food and shelter, and may attract and harbour some pests. Shelterbelt plantings in semi-arid areas may have the desired micro-climatic effects, but may also have negative side-effects such as root invasion of adjacent crop lands and of irrigation drainage tiles. Shelterbelts may waste water intended for crops by withdrawing water from irrigation ditches.

Wildlife and Fisheries

Logging can injure and kill some animals outright, but more likely it damages or destroys key habitats such as nesting sites, including old hollow trees, feeding and breeding grounds. It can also interrupt or eliminate the aerial pathways of arboreal species that seldom move at ground level. Some endemic species of animals could be eliminated altogether.

Erosion, sedimentation or improper slash and other waste disposal can damage or destroy fish spawning and nursery areas, benthic communities and other important aquatic habitats and organisms. Turbidity can interfere with light penetration and thereby decrease the rates of photosynthesis and of overall productivity of aquatic ecosystems. Removal of tree cover adjacent to streams and rivers can raise the temperature of water to levels injurious to aquatic organisms adapted to stenothermal conditions. Log floating can interfere with commercial and subsistence fisheries by damaging fishing gear, aquatic habitats and by contaminating waters with wood preservatives. Log and log hauling can displace animals through noise and increased human presence; some of these animals, particularly if highly territorial, cannot easily occupy adjacent undisturbed forests. Displaced animals added to existing populations can mean crowding, with related stress and decrease in reproductive rates.

The elimination of some herbivores, birds or insects through logging can interfere with the regeneration of tree and other plant species that depend on these animals for pollination or seed dispersal. Elimination of some insect populations could retard the digestion of vegetal matter and, hence, nutrient recycling. Clear-out areas and forest roads create new access which, if uncontrolled, can load to excessive hunting or poaching in hitherto inaccessible areas.

Logging can create favourable new browse or habitats for some animals, notably some wild cattle, other ungulates and rodents. Some herbivores, especially elephants, can be displaced and made dependent on agricultural crops, with resultant economic losses. The new habitats created by logging can result in the explosive growth of some animal populations, primarily rodents, some herbivores and some insects. These animals can, in turn, adversely affect forest regeneration or nearby crops. Some of these animals can be vectors for diseases.

Local Cultures and Subsistence Economies

Forestry projects can substantially and permanently improve the living standards of local residents through direct and indirect employment in a new cash economy, new roads, housing, medical facilities and other new infrastructure.

However, the transition from a non-gash to a cash economy and from a traditional life-style to a more modern one may or may not be the desired goal of most local residents. If the preservation of a subsistence economy is the expressed wish of the local population, then forestry activities can have a number of detrimental effects. Thus, logging can eliminate or reduce the habitat, food and other traditional resources of forest dwellers. In remote areas, logging operations and the attendant influx of outsiders and new ways can lead to "culture shook" and related social disintegration. At worst, it can lead to violent conflict. Logging can inadvertently or other wise damage or destroy trace, sites or other landscape elements that have religious or other heritage value. It can disturb burial grounds a and historic or archaeological sites.

The elimination of traditional food and other supplies, the creation of new demands, or the introduction of fossil fuels and other consumer item can disrupt a local non-cash economy, thereby causing social upset. Deforestation can decrease the local fuelwood supply and thus make residents dependent on substitute energy sources, with regional or even national repercussions. Afforestation or reforestation can reverse this trend. Forestry activities can raise employment and other socio-economic expectations among people who wish to leave the non-cash economy; these expectations, if not met, can lead to conflict. Logging and improved access can increase the extent and intensity of shifting cultivation, with resultant degradation of soils, vegetation and other resources.

Demographic-Economic Expansion

Forestry projects can stimulate the local cash economy through direct and indirect employment and increased demand for goods and services. These projects can also result in improved facilities, such as new or better roads, medical facilities, schools etc. Balanced against these benefits may be the need to clear additional forest for logging camps, new settlements, roads and other facilities. If poorly regulated logging camps can be a source of friction with local residents. Improper waste disposal and harassment of wildlife are often associated with temporary camps. The same applies on a larger scale to new settlements created by the influx of people directly or indirectly employed in the forestry sector.

In general, more people mean more roads, schools, waterworks, liquid and solid waste disposal and other facilities that may create jobs but also overtax local financial and trained manpower resources. Greater concentrations of people and economic activity also mean pressures on the local and regional environment (demand for recreational space, degradation of air and water quality, inroads into animal habitats, etc.). The demand for public services (education, health, government) is also likely to increase; this can have benefits such as job creation, but also negative impacts if the necessary trained manpower is not available.

Expansion of forestry activities may conflict with or complement other economic land uses such as agriculture, mining or tourism (cf. Conservation).

Epidemiology

Forest removal may increase the rates of incidence of certain diseases or introduce new diseases such as malaria (through exposure of stagnant water previously under forest cover) and scrub typhus (creation of Imperata grasslands invaded by rodents). Any water impoundment associated with forestry could lead, in certain regions, to outbreaks of schistosomiasis or onchocerciasis. Destruction of forests may bring forest arthropod vectors of arbovirus diseases into closer contact with man. On the other hand, clearing of riparian forest is used to control trypanosomiasis. The influx of forest workers and outsiders may increase the incidence of certain diseases such as trypanosomiasis or sexually transmitted diseases. On the other hand, medical facilities and standards established in connection with forestry projects can significantly improve local or regional health conditions.

It is conceivable that, with deforestation and/or penetration of agriculture into forested areas, domestic animals become the hosts of parasite cycles previously hosted by forest animals.

Conservation

Forestry activities may conflict with existing, planned or potential conservation areas (protection forests, parks, game reserves, strict nature reserves, sanctuaries). Logging could affect conservation areas of vague legal status or that are poorly delimited on the ground. Forestry activities in the buffer zones around conservation areas may have indirect detrimental effects (sedimentation; displacement of animals through noise and human presence; increased poaching due to new access). Logging can undermine conservation plans if it takes place while these plans are being held up by administrative or legislative delays.

Turbidity in streams dead trees, swaths of clear-cut areas, accumulations of slash and other debris, hanging debris, road traffic from logging areas, noise, dust and other side effects of forestry can detract from the amenity value of a region.

On the other hand, well planned forest roads can subsequently be used for tourist and other amenity uses, as well as for enforcing conservation laws.

Re- or afforestation, especially if done from a multiple purpose standpoint, can add to the amenity value of a region, either through improved aesthetics, the provision of recreational spaces or climatic improvement. Plantings in bare or eroded landscapes greatly improve the appearance of those landscapes, in addition to providing many other environmental benefits. However, plantations that are too regular or uniform in species composition can be a visual liability.

Cut-over areas or monotonous plantations well outside conservation arose such as national parks can detract from vistas that are appreciated from points within those areas.