Environmental and social benefits of bio-mass plantations :

Woody crops bring in economic rewards

Dr N Yogaratnam

Tree bio-mass plantations potentially offer many direct and indirect environmental benefits, but they may have negative environmental impacts as well. Ascertaining the environmental impacts are complex because the impacts of using bio-mass for energy must be considered in the context of alternative energy options while the impacts of producing energy crops must be considered in the context of alternative land uses.

Environmental

Gobally significant environmental benefits may result from using wood for energy rather than fossil fuels. The greatest benefit is derived from substituting biomass energy for coal. The degree of benefit depends greatly on the efficiency with which the wood is converted to electricity. If the efficiency of conversion of wood to electricity is similar to coal conversion to electricity then the benefits are several. Airborne pollutants such as toxic heavy metals, ozone-forming chemicals, and releases of sulfur that contribute to acid rain will be reduced.

The ash and waste products from burning will, in most cases, be sufficiently benign to return to the soil. There will be a considerable reduction in net carbon dioxide emissions that contribute to the greenhouse effect. For example, one dry tonne of wood will displace 15 GJ of coal. The 15 GJ of coal will have the equivalent of 0.37 tonnes of carbon assuming the wood is converted at an efficiency of 25 percent.

Feedstock carbon ( seeTable1) is the carbon embodied in the biomass or the carbon sequestered by plant growth. Input carbon is the carbon embodied in the factor inputs (e.g., diesel fuel) used to grow, harvest, and transport the biomass.

National

National level significant environmental benefits can be maximized when tree biomass plantations replace annual crops, heavily grazed pastures, or degraded lands. Benefits can include:

1. protection of water quality,

2. reduction of floods during wet seasons and maintenance of water supplies during dry seasons,

3. erosion prevention,

4. improvement of local microclimate through evaporative cooling and humidification,

5. wind breaks and shelters that reduce erosion and conserve water, particularly in dry regions,

6. reduction of fire danger,

7. reduction in use of fertilizer and agricultural chemicals,

8. improvement of soil properties, and

9. protection of wildlife and other components of biodiversity.

Negative effects

Negative environmental effects of plantations may occur locally if unmanaged natural forests or forests managed for low intensity uses are removed and replaced with short-rotation biomass plantations. Negative impacts can include:

1. increased erosion and reduction of water quality as a result of forest harvesting;

2. increased rates of runoff and decreased water-holding capacity;

3. increased chemical pollution from fertilizers and pesticides;

4. degradation of soil quality and productivity; and

5. reduction of biodiversity through alteration of forest structure, creation of tree monocultures, and use of non-native tree species which local wildlife are unable to use.

Guidelines Concern over possible negative impacts has led environmental groups at both national and international levels to attempt to establish environmental guidelines prior to the commercialization of biomass energy technologies. In Brazil, early mistakes in establishment of Eucalyptus plantations, along with increasing environmental sensitivity, have led to substantial regulation of the forest industry.

To minimize or avoid negative impacts from energy crop production, most proponents of biomass energy are recommending that biomass plantations be established on existing agricultural lands or degraded lands. Forestry codes and plantation management procedures currently being developed and implemented around the world generally prohibit the conversion of natural forest to forestry plantations.

Many of the natural forests occur on relatively poor soils, and destruction of natural forests is now recognized to have environmental costs in terms of biodiversity, environmental quality, and economic sustainability that far outweigh short-term economic gains from forest clearing. Principles recently formulated in the U.S. for the wise development of biomass resources include the following:

Biomass energy system development must be guided by consistent decision criteria and should foster the multiple goals of environmental protection, economic revitalization, and energy security. iiiEnergy crop production practices and energy conversion technologies must be selected to ensure that the use of biofuels substantially reduces anthropogenic emissions that may contribute to global climate change. The use of biofuels should not exacerbate greenhouse gas emissions when compared with conventional fuels on a full-fuel cycle basis.

The development and management of biomass resources should protect and, wherever possible, enhance ecological integrity and biological diversity, while minimizing adverse impacts to land, air, and water.

The development and management of biomass resources should contribute to the economic well being of producers, local communities, and the nation as a whole.

The use of biomass resources for energy purposes must rationalize trade-offs in terms of competing uses for the land and plants (whether for food, fiber, recreation, wildlife habitat, or other uses), while also recognizing the impacts and trade-offs implicit in the use of other energy resources.

Soil/water Issues

The beneficial effects of forests on water quality, soil erosion prevention, and the reliability of water supply have long been recognized. Many natural forest reserves have been established around the world in mountainous areas for the protection of municipal water supplies. Biomass plantations can also serve this purpose, particularly if the negative effects of harvest on soils and water supply can be minimized. Plantations are particularly valuable in improving the water supply on land that has been degraded by deforestation or desertification.

The positive effects of plantations on soil and water conservation results primarily from protection of the soil surface from the direct impact of rain and from the improvement of soil structure through root penetration and the addition of organic matter from decomposing leaves, roots, and wood. In comparison to either crops or bare soil, forest greatly reduces the proportion of rainfall that is lost as runoff, thus leaving much more water available to feed springs and streams during dry periods.

The positive effects of trees on water retention tend to increase over time, so long rotations and practices that enhance organic matter input into the soil are particularly favorable.

Variation

Tree species vary greatly in their effect on soil properties and on water cycling. Some tree species, such as E. globulus and E. tereticormis, tend to use water very rapidly, leading to reduced water yield from watersheds, stress during dry seasons, and creation of unfavorable conditions for interplanting with food crops. On the other hand, studies on Eucalyptus grandis in Brazil have found the annual variation in soil water to be similar to that for Pinus caribea and savanna-like native forests.Tree plantations have also been shown to reduce wind erosion, reduce evaporative losses of water, and improve soil moisture conditions sufficiently to allow cropping on degraded lands. Nitrogen-fixing species, such as acacias and leaucena, can improve the soil, reduce the need for expensive nitrogen fertilizer, and produce fodder for farm animals.

A primary difference between short rotation plantations, and forests harvested for timber with regard to erosion and water issues is the frequency of harvesting and replanting. Because 40 percent of tropical rainfall falls at erosive rates (greater than 25 mm/hr), soils exposed during and after harvesting are susceptible to serious erosion. Harvesting and reestablishment practices thus become a very important determinant of the potential for environmental damage. When reestablishment occurs through coppice re-sprouting, risk of soil loss is minimized by rapid re-growth. The use of cover crops or grass strips between the rows can reduce erosion when replanting is required.

The potential for soil loss increases greatly with increasing precipitation and on hilly or mountainous land In general, tropical soils are much more subject to degradation from harvesting than forests on younger soils, such as those found in much of the temperate zone.

Biodiversity

Concern about the loss of biodiversity is based on the idea that each organism, even those that are unknown and unnamed, has some value. Many plants and animals are valued for the medicinal chemicals they produce or for their importance to forestry or agriculture. Other species are valued for their beauty or other special properties. Many species, even obscure organisms in the soil, may play important but poorly understood roles in improving soil fertility, in preventing diseases and pests from affecting crops, or otherwise maintaining a balance of nature that is favorable to human existence.

For these and many other reasons, there is a broad consensus among scientists, citizens, and politicians that biodiversity should be preserved by preventing the extinction of species wherever possible. Because many birds, mammals, insects, and other animals depend on one to several particular tree species, extensive biomass plantations of a single tree species can be extremely destructive to biodiversity when displacing natural habitats. Clearing natural forests to establish plantations usually destroys biodiversity and should be avoided.

Many of the forests with high biodiversity occur on soils that are too poor to support productive plantations, so there is usually no economically or biologically sound reason to replace them with plantations. Establishment of plantations on degraded lands that were previously deforested will usually have a positive effect on local biodiversity by improving the habitat for plants and animals that cannot survive deforested areas and may have other benefits such as improvement of water quality and quantity and soil improvement.

Non-native species

There is considerable controversy on the use of non-native species on the scale that might be required for biomass energy. Plantations based on non-native species, such as eucalyptus outside of Australia and teak outside of Asia, are generally believed to provide little suitable habitat for native animals, although research on this issue is continuing.

Depending on the planned energy conversion technology, plantations for biomass may be able to utilize a wider variety of tree species and thus may support a higher biodiversity of plants and animals than single-species hardwood or pulp plantations that must produce a crop that is extremely uniform in form and other properties.

Properly designed plantations should include areas of natural vegetation, appropriate wooded buffers for waterways and corridors for wildlife movement, as well as protection of historical areas.Since the 1960s Brazil has required forest companies to either leave 10 percent of the managed area in natural vegetation or ensure that 1 percent of the trees planted are native species. The 10 percent option has normally been preferred and has resulted in positive benefits for both bird diversity and insect pest control. Specific guidelines developed by the National Biofuels Roundtable in the United States for improving habitat are: iiiMatch native ecosystem cover types as much as possible (e.g., perennial grasses in prairie regions and trees in woodland regions). In addition, emulate natural vegetation patterns and functions when establishing energy crops on agricultural lands.

Locate, plant, and harvest tracts of energy crops in ways that help improve pathways for animals to move between habitats and across landscapes in any particular year. Employ energy crops in ways that minimize the fragmentation of desirable habitats and improve overall habitat quality of the landscape for native species.

Chemical Pollution

The previous use of the land will determine the extent to which chemical pollution is an issue. Plantations generally require fewer inputs of fertilizers, herbicides, and pesticides than more intensive forms of agriculture. In regions of extensive agricultural activity where non-point pollution of streams is a problem, tree plantations may improve water quality by serving as a filter of agricultural chemicals.

Establishment of plantations on pasture land, as may occur in many parts of the developing world, would result in additional use of some chemicals unless hand labor is used to control weeds. Methods are available to minimize chemical use such as mulching and applying chemical only in strips around the trees though the relative costs of these measures have not been well established. Pest control can occur with minimal chemical use if frequent monitoring and biological control methods are used. The most effective method of pest control is to maintain ongoing breeding and genetic selection program so that susceptible trees can be eliminated and replaced with resistant varieties. Brazilian pulp and paper companies have been successful in controlling pest problems though genetic selection programs.

Social Economics

Successful woody crops can provide multiple economic, social, and environmental benefits to a country if properly planned and integrated into the multiple land use opportunities within the country. In regions where the amount of good quality soil is limited, use of the best soils for biomass crop production will displace other land uses.

The concern expressed most often is that use of land to produce biomass crops will reduce food availability. Such a concern was expressed in the mid-eighties when sugarcane establishment was accelerating in the agricultural state of São Paulo, Brazil as a result of subsidies provided by the National Program for Alcohol production (commonly referred to as Pro-Alcohol). With 64 percent of the sugar cane expansion in the state of São Paulo occurring on pasture land owned by large land-holders, displacement of primary food production was not the major issue.

Tree plantations always exist in a social and cultural setting based on the inhabitants of the area before the plantation was created, and the inhabitants who arrived after the plantation was established. To be economically successful, and to avoid negative effects on society and the natural environment, each plantation must be designed for its own specific social, cultural, and environmental setting. Factors that must be considered include

1. pre-existing land uses;
2. local agricultural practices;
3. local political systems;
4. local cultural divisions of labor and authority between men and women;
5. local traditions of land tenure and stewardship including private property right; and
6. local cultural values.

Local community

Because plantations must depend on local labor, it is desirable to maintain the structure of the local community in a way that provides a steady supply of reliable workers. The more the plantation can be integrated into the daily economic and social life of the community, to the mutual benefit of both the community and the plantation, the more likely it is to succeed in the long run.

For this reason, Brazil and China are leaders in investigation of agro-forestry techniques for large scale use. Tree establishment can be enhanced, and the need for dangerous chemicals reduced, through the inter-planting of agricultural crops during the first years after planting. This type of agro-forestry benefits the plantation as well as the local community by providing food and/or cash crops.

Multipurpose trees

The use of multipurpose trees that provide energy products, animal fodder, and enrich the soil through nitrogen fixation are viewed as the ideal energy tree. It is likely this is the reason that leucaena was the species selected for use in the Philippine Dendro-thermal program. Research has continued around the world on leucaena, acacias and other nitrogen fixing trees such as black locust.

However, there has been an unfortunate tendency for these species to be susceptible to insect pests. Leucaena plantings have largely been destroyed by a pest and black locust is susceptible to a stem borer. These problems may be solved through genetic selection, biotechnology or biological control agents, but at present, the widespread planting of nitrogen fixing trees for energy or pulp is not occurring.

Even so, the multipurpose tree concept is a good one that deserves continued consideration. One success story is occurring in Brazil with a company that has a specialized conversion technology to produce pulp, alcohol, cattle feed and even electricity from a bamboo (Bambusa vulgaris) species.

In conclusion, plantations for production of biomass energy have numerous potential environmental benefits.

If energy crops are included in the general mix of agricultural crops in a considered and informed way, environmental damage can be avoided; in fact, there could be significant environmental and ecological benefits achieved in tandem with the development of a fully sustainable energy resource.