The following paper will soon be published in the proceedings of “Planted Forests: Contributions to Sustainable Societies” College of Forestry, Oregon State University. Portland, Oregon June 28-July 1, 1995.
How Can We Feign Sustainability With An Increasing Population?
David B. South, email@example.com
School of Forestry and Alabama Agricultural Experiment Station, Auburn University,
Auburn, AL 36849-5418, USA
Attitudes of human societies towards tree plantations can be a critical factor in determining the source of wood supply in the future. Since human populations will expand substantially in the southern hemisphere, considerable increases in the demands on native forests will occur. Currently, only a limited amount of tree plantations have been established specifically to provide firewood in developing countries. This may be due in part to a world society that has evolved a general preference for pastures but aversion to tree plantations. In total, pastureland and tree plantations amount to 26% and 1% of the world’s landbase, respectively. Nevertheless, our actions today will determine if children in the future collect firewood from natural stands or from tree plantations. It is estimated that a substantial afforestation program could increase the amount of tree plantations to equal 5% of the world’s landbase by the year 2050. Ten billion dollars (U.S.) is a rough estimate of the annual costs for such a program (assuming no overhead or administrative costs). Most of the wood needs could come from these plantations. However, if the world’s society wants most wood in 2050 to come from natural stands (>80%), then tree plantations can be limited to just 1% of the landbase.
Keywords: population growth, carrying capacity, plantations, firewood
The world population for 1995 is about 5.7 billion. If the population continues to increase at a rate of 1.5% per year, the population will double before the year 2100. Some estimate 11.2 billion by the year 2100 (World Resources Institute 1992). If the per capita consumption does not change, the world consumption of wood could be greater than 7 billion cubic meters (m3)/yr by the end of the 21st century. This wood will come from an increase in harvesting of natural stands and/or from plantations. The amount of wood that is harvested from natural stands in the future will depend directly on the amount of plantations we establish today. Instead of planting more trees to provide wood for a population of 10 billion, many countries are reducing their rates of tree planting. For this reason, the following hypothetical word problem is provided to illustrate how a society’s views regarding land management can affect the wood supply for future generations.
In the Hypothetical Ocean, there are three islands that are identical in size and natural resources. Each island is 12 hectares in size and is covered with 10 hectares of woods (the beach covers about 1 hectare and there is 1 hectare of high ground). Each island is inhabited by a different society. Each society has the same ideas about population growth, food consumption and wood consumption. However, each society has a different view about how to manage the land for future wood needs. Initially, each society has 10 people at year 0. Each society follows a strict ethic regarding population growth. Therefore, population growth is limited to only 2 persons per year per island.
Each society obtains all the food they need from the ocean. However, they need wood for cooking and heating. Firewood is consumed at a rate of 1 m3/person/yr. The woods produce about 24 m3/yr and this wood can be collected on a sustainable basis without reducing the growing stock. However, the trees are small and therefore the standing volume of the forest never exceeds 2.4 m3/ha. To clarify, the 10 hectare forest has 24 m3 of wood on January 1st and during the year, 24 m3 of firewood (dead branches, etc.) can be collected. On December 31, the standing volume of the forest is still 24 m3. If the firewood is not collected, the branches fall off the trees and either decay or are occasionally washed off the island. However, firewood can be collected and stored indefinitely (in a dry, high place) without wood decay. If harvesting reduces the standing volume to less than 24 m3 the annual firewood production will only equal the standing volume on January 1st (for ease of calculation).
Each society has the same major objectives: to keep cooking food and to keep at least 5 hectares of woods as a preserve. Although firewood can be collected from the preserve, the objective is to not reduce the standing volume on these 5 hectares.
The three societies differ in the way they decide to manage their island. Society A decides to keep all 10 ha of woods in a natural state and collects all the firewood from the woods (24 m3) and store any unused firewood for future needs. On January 1st (year 1), they have 14 m3 of firewood is in storage.
Society B decides to cut down 5 hectares of woods and puts the wood in storage. On the cleared land, a 5 hectare plantation is established using an exotic species (Salix spp.). The willow plantation is harvested each year and produces 10 m3 of firewood/ha/yr. On January 1st (year 1), there is 64 m3 of firewood in storage (50 m3 from the plantation, 12 m3 from cutting down 5 hectares of woods, and 2 m3 of extra firewood collected from the preserve). They plan on continuing to manage the 5 hectares of willow plantation on a sustainable basis (adding kelp for fertilizer to maintain production at 10 m3/ha/yr).
The society on island C does the same as the society on island B. On January 1st, (year 1) they also have 64 m3 of stored firewood. However, they decide to invest time and effort into research. Although they make some mistakes, new ways are discovered to increase the volume production from the willow plantation. Amazingly, each year the researchers figure out a way to increase willow production by 0.2 m3/ha/yr. For example, the first willow crop was 50 m3, the second was 51 m3 the third was 52 m3, etc. With the information given, how long does it take before each society depletes the storage of wood? Which society is most likely to protect the 5 ha preserve for the longest period of time?
Island A can only sustain a population of 24 people (i.e. 24 m3/yr). By storing firewood collected from the natural wood, the supply of stored wood runs out during year 14. On January 1, year 15, there are 40 people on the island and during the year they consume 24 m3 of growth for the year, and end up cutting down 6.7 ha of the woods. On year 16, there is only 3.3 ha of woods remaining, which is not enough to supply 10 people (much less 42). The low productivity of the non-preserve land limits the ability to protect the preserve.
The society on Island B increases the production of firewood with a willow plantation. With both wood from the plantation and wood from the preserve, this society is able to produce 62 m3/yr. Therefore, Island B can sustain a population of 62 people (two and a half times higher than Island A). When combined with storage, the society lasts for 51 years before the supply runs out. The preserve was protected for more than 3 decades longer than island A.
By investing time and effort in research, the society on island C was able to find ways to increase volume production per hectare. As a result, their preserve was protected for more than a century. By conducting research aimed at improving yield, this society was able to have a 5 ha preserve and sustain at least 190 people (a yield of 190 m3/yr could be obtained on year 116). However, at year 104 the population is 218 and the amount of wood in storage is down to 12 m3. They decided that, for the next year, some of the 5 ha “preserve” would need to be converted to a willow plantation in order to supply enough wood for everyone. To meet the needs of 220 people, they expand their plantation by 2 ha.
The ability to protect the preserve varied with the management regimes adopted by the society. Societies that relied on plantations to supply part of their wood needs were able to keep a preserve intact for much longer than the society that relied entirely on native woods. One could conclude that high productivity on non-preserve land can help to protect the reserve by meeting the day-to-day consumption needs of the population. I conclude that high productivity from intensively managed lands can help protect wilderness or non-utilized lands from exploitation. Likewise, agronomists have concluded that increasing productivity on the current agricultural lands can feed 10 billion people without increasing the amount of farmland (Waggoner 1994).
None of the societies can sustain a population growth of 2 persons/yr. Therefore, the real problem for all three societies is population growth. Adoption of new technology can delay the inevitable, but for areas with limited resources, societies must adopt appropriate ethics about population growth if the society hopes to be sustainable during the next several millennium. From this exercise, it also can be concluded that for any of the three islands to have a sustainable ecosystem and an unconstrained population growth either (1) per capita wood consumption must decline in direct proportion to the population growth (through recycling, product substitution, or reduced standard of living), or (2) technology must devise ways to continually improve yields.
Even when population growth is linear, limited resources cannot sustain unlimited population growth. I realize this statement does not agree with others (Barnett and Morse 1963; Manthy 1977; Simon 1977; 1981; 1992). I imagine that Julian Simon would propose a fourth island where researchers were able to increase growth (each year) by 0.6 m3/ha/yr. This rate of improvement would be more than enough to support the population growth and would eventually allow the natural preserve to expand in area. Simon (1981) has stated that “if the past is any guide, natural resources will progressively become less scarce, and less costly, and will constitute a smaller proportion of our expenses in future years. And population growth is likely to have a long-run beneficial impact on the natural-resource situation.” While I agree with much of Simon’s philosophy, I do not accept a cause and effect relationship between population growth and the supply of firewood. Just because wood supply increased from year 0 to year 50 as the population of island C increased, we should not assume that wood supply will continue to increase for the next 50 years.
Although the islands in the word problem are fictitious, real islands and/or countries exist to illustrate each management type. Island A is similar to what happened on Easter Island. Around 400 AD, people arrived on an island that was covered with trees and palms. A society emerged that is well known for statue building. However, as the population increased, the consumption of natural resources increased. It is estimated that forest clearance began around 700 AD and the last remnants of the forest were gone by about 1400 AD (Bahn and Flenley 1992). Initially, the society had wood to build large canoes, but by 1722, wood was so limited that the few remaining canoes were small (3 m long), frail, and leaky. By 1770, Gonzales wrote, “Not a single tree is to be found capable of furnishing a plank so much as six inches in width.” Although the society apparently did not plant trees for their children, they often promised to send their children a tree from the afterlife (Bahn and Flenley 1992). Bahn and Flenley believe the social catastrophe that occurred in the 1700s was a direct result of over-exploitation of the forest. I do not believe the population growth on Easter Island had a long-run “beneficial” impact on the natural-resources of the island. Although the islanders may have invested research into how to move large statues, they likely did not invest time into determining how to propagate non-food trees.
Although Alabama (in the southern United States) is not an island, it can be used as an example of a society which is similar to Island B. Prior to 1900 AD, this society relied heavily on wood as a fuel source, but today fossil fuels are used to cook food and heat homes. Large tree planting programs during the late 1950’s and late 1980’s converted old agricultural land to pine plantations. Today, approximately 10% of the landbase is in plantations (1.4 million ha) and 56% is in native woodlands (Williams 1992). Currently, about one-third of the softwood harvested is from plantations. Although more plantations are expected to increase in the future, only a few forest scientists in Alabama are currently exploring ways to increase the wood yields (i.e. mean annual increment). With a population of over 4 million, only about 8 researchers in Alabama are actively looking for ways to improve plantation yields. Currently, production of pine plantations is about 10 m3/ha/yr.
New Zealand can be used as an example of Island C. Currently, these islanders have established tree plantations (1.3 million ha) on about 5% of the landbase and have retained 23% of the land in native woodlands. Today, about 98% of the wood harvested is from plantations. This reliance on wood from plantations is mostly a result of large tree planting programs conducted during the 1930’s and again from 1970 to the late 1980’s. With a population of 3.8 million approximately 30 scientists are working to improve plantation growth. Currently, production of pine plantations is often about 24 m3/ha/yr.
The purpose of the word problem and the “real world” examples is to illustrate the “yin-yang” aspects associated with tree monocultures and native woodlands. Some people believe that a dualistic philosophy is superior to the “all or none” philosophy touted by others. The important question, I think, for a population of 10 billion, is how much land do we want to devote to each of the major cover types (wilderness, native forests, tree farms, pasture land, farm crops, roads, cities, etc.)? This seems more relevant than debating the pros and cons of either having all natural forests or all industrial plantations.
Some ecologists believe the concept of carrying capacity is directly relevant to the realistic evaluation of the future size and impact of human populations (Pulliam and Haddad 1994). Perhaps now is the time for foresters to make an attempt at defining the “carrying capacity” for wood production. As a society, foresters are concerned about population growth and its effects on natural resources (see Appendix). Although estimates of annual wood consumption are increasing, do we know how to provide a sustainable wood supply for a population level of 10 billion people? In just 11 years, the consumption/production of roundwood in developing countries has increased by about 25%. In just 15 years, the world’s roundwood consumption will approach 5 billion m3/yr (FAO 1995). If this rate of wood use per capita is maintained, and the population continues to increase as expected, then by the year 2050 the world might be consuming about 7 billion m3/yr. This level of consumption is about 75% greater that today (1995) and assuming a low level of plantation establishment, this rate of harvest will likely exceed the maximum level of sustainability. Historically, deforestation occurs as rural populations increase (Clawson 1979; Inman 1993).
As a forester, I realize the net annual increment (NAI) is not the best scientific estimate of how much wood our world can supply indefinitely. However, since I believe we are not planting enough trees for the future, I will use the ratio of NAI to annual harvest as a rough indicator of “sustainability.” If the NAI for developed countries is 2.4 billion m3 (FAO 1995) and we assume that the NAI for developing countries is 2 billion m3/yr (not all forests are “production” forests), then a very rough estimate for the total NAI for 1990 is near 4.4 billion m3 . If the demand for wood in 2015 will be 5 billion m3 (FAO 1995), then deforestation will likely result in developing countries where the annual harvest will exceed the NAI due mostly to a high demand for firewood. The demand just for fuelwood and charcoal in developing countries is estimated to be 2.4 billion m3/yr by the year 2010. By the year 2050, the demand for firewood (perhaps not the supply) could reach 3.3 billion m3/yr.
What type of world society (A, B, or C) will help ensure our children do not end up exploiting the world’s forests? Assuming we consume wood only from sustainable systems, where will the extra wood be produced? Do we want the extra 3 billion m3 to be logged from only from natural stands, or do we want most of the additional wood to come from plantations? If most individuals are from a society similar to Island A, then the “politically correct” policy would be to harvest wood mainly from native woods. Some individuals from this society would not favor the expansion of plantations and would likely protest allocating 5% of the landbase for plantations.
However, individuals who are from societies where plantations comprised 5% or more of the landbase (e.g. Alabama, Japan, New Zealand, Sweden) would see no problem with using 5% of the landbase for tree farms and fiber farms. Individuals from these societies would believe the “correct” policy would be to establish plantations to provide a renewable resource to sustain the society for a much longer time period.
Estimates on the total amount of land in tree plantations can vary widely. However, a recent estimate is 128 million ha (Brooks 1993). Over the past 15 years, plantations have been expanding at a rate of 2.4 million ha/yr. If this rate continues for the next 60 years, then the world would have 272 million ha of plantations in 2050. This would be equivalent to 2% of the world’s landbase. Assuming that 20 years is an average rotation length for plantations, a total planting rate (for 1990) would be approximately 9 million ha/yr and a final planting rate (2050) would be 16 million ha/yr. Estimates for annual planting rates vary from 4 to 14.5 million ha/yr (World Resources Institute 1986; 1992; Sedjo 1995).
If the world’s society decides to set a goal of 630 million ha of plantations by the year 2050 (about 5% of the landbase), the expansion rate for plantations would need to be about 9 million ha/yr (as opposed to a current expansion rate of 2.4 million ha/yr). The total annual planting rate would initially need to be approximately 15 million ha/yr. At year 2050, the annual planting rate might be closer to 33 million ha/yr. In contrast, if our society decides to limit plantations to just 1% of the world’s landbase, then the annual planting rate would drop to about 6.5 million ha/yr (assuming an average rotation length of 20 years).
Table 1: Population and plantation areas for 1990 (Brooks 1993), estimated populations for the year 2050, and proposed plantation areas for the year 2050 (assuming 93% of wood needs come from plantations). Plantation expansion rate does not include replanting of harvested plantations.
million ha …. % of landbase
|Plantation expansion rate|
Note: assumes a per capita consumption rate of 2.4 m3 of wood for Canada and United States; 0.9 m3 for Europe and Japan ; 0.5 m3 for Africa, Asia, and Latin America.
Currently, the U.S. has about 1.5% of the landbase in plantations (Table 1) and the annual planting rate is about 1 million ha. If the average rotation length in the U.S. is 30 years, and the planting rate remains at 1 million ha/yr, then we should eventually reach a plantation acreage of 30 million ha (about 3.3% of the landbase). In the southern U.S., there may be 20 million ha of plantations by the year 2030 (USFS 1988). By using plantations, it is expected that roundwood consumption in the U.S. will increase by 40% even though the amount of exploitable timberland decreases by 4%. If the U.S. society wants to produce 960 million m3/ha/yr from plantations by the year 2050, then about 96 million ha of plantations would be required. This would require expanding the plantation acreage by 1.4 million ha/yr. Initially, this would require a planting rate of 1.8 million ha/yr (but would end up with a planting rate of about 3.2 million ha/yr). Since almost 1.4 million ha/yr were planted in 1988, planting 28% more should not be too difficult. If these goals were met, the U.S. would have about 11% of the landbase in plantation by 2050. Using current planting rates, some predict 20% of Alabama’s landbase will be in plantations by the year 2030. If all the additional U.S. plantations were established on pastureland, then the amount of pastureland in the U.S. in 2050 would decrease to about 16% of the landbase.
Table 2. Two possible wood production scenarios for the world in the year 2050. The native stand scenario estimates 86% wood harvested from managed native stands. The plantation scenario estimates 93% wood harvested from plantations.
In the past, the world’s society prefers to establish pastures to tree plantations. Except for Japan and Sweden, the ratio of pastures to plantations is very high in most countries. In just 33 years, (from 1955 to 1988) pastureland increased globally by about 1 billion ha while tree plantations increased by about 0.1 billion ha (a ratio of 10 to 1). Pasturelands have been allowed to increase from 18% of the world’s landbase in 1955 to about 26% in 1990. In contrast, it seems unlikely the world’s society would allow tree plantations to increase from 1% of the world’s landbase in 1990 to 9% in just 33 years (from 1995 to 2028). The amount of printed words (mostly in newspapers and magazines) objecting to establishing tree plantations seems much greater than the number objecting to the establishment of pastures. Owing both to increasing population pressures and the preference for eating red meat, it is likely that during the next 55 years, more natural forests will be converted to pastures than will be converted to tree plantations. This will occur even though overgrazing can cause soil degradation (while tree plantations can be used to restore degraded land). According to the World Resources Institute (1992):
“Overgrazing by livestock decreases vegetation, exposing the soil to water and wind erosion. In addition, livestock trample and thereby compact the soil, reducing its capacity to retain moisture. Overgrazing is the most pervasive cause of soil degradation, affecting 679 million hectares (35 percent of all degraded land). In Africa and Australia, overgrazing causes 49 percent and 80 percent, respectively, of soil degradation, mainly in semiarid and arid regions.”
Let’s examine two possible management scenarios for the world. The “native stand scenario” would keep tree plantations at the current level of about 130 million hectares (1% of the world’s landbase). This would allow pastures to increase to about 28% of the landbase. Although most of the wood will be harvested from native stands, about 18% would be supplied by plantations (Table 2). Over half the wood consumption would be used for firewood.
In contrast, the “plantation scenario” would increase the amount of plantations to about 5% of the landbase (Table 1) but would decrease the amount of pastureland to 22% of the landbase. Most of the wood produced from this scenario will be harvested from plantations. Only about 7% of the wood would be supplied by managed native forests. Although about 130 million ha of afforestation would be for biomass energy (Sampson et al. 1993; Wright and Hughes 1993) gain, about 260 million ha would be for firewood production in developing countries.
All of the “new” plantations could be established on pastureland (i.e. afforestation). Removing 500 million ha of degraded pasturelands would still leave 22% of the world’s landbase in pastures (about the 1965 level). This might reduce the production of pasture feed meat by 15% or less. However, it is likely that some societies will not support the establishment of plantations on pastureland. Some will claim the economics favor production of red meat instead of trees. Some will object to plantations if it displaces the traditional sources of livelihood for local people (Barber et al. 1994). Some may argue that a monocuture of trees is more harmful to the environment than a monocuture of monocots.
If productivity of plantations is substantially higher than for native woodlands, then an increase in plantations should remove some of the pressure from natural stands. I have assumed that tree plantations can average about 10 m3/ha/yr and natural woodlands will produce about 2 m3/ha/yr (Table 2). In the southeastern United States, native hardwood stands produce about 2.5 to 3 m3/ha/yr (U.S. Forest Service 1988). For the Commonwealth of Independent States, an average MAI is estimated at 1.4 m3/ha/yr (Richards 1987). Some tropical forests in the Asia-Pacific region may produce 1 m3/ha/yr on a sustainable basis (Sedjo and Lyon 1994). Although higher values for individual regions can be obtained, 2- and 10 m3/ha/yr are rough estimates of average production on a global basis (and therefore should not be viewed as accurate estimates).
Approximate costs for establishing plantations are provided in Table 3. The costs vary due to differences in labor costs, seedling costs, and site preparation costs. If a cost of $830/ha is used as a median value, then a planting program aimed at establishing 12 million ha/yr would cost 10 billion dollars. This is only half the amount some recommended for afforestation and soil conservation (World Development Report 1992). This would be less than $2 per person/yr. In comparison, one U.S. nuclear submarine can cost 2.5 billion (the U.S. Senate is considering building 30 new nuclear-powered submarines over the next 20 years). Currently, the payment on interest for the U.S. debt amounts to about $775/person/yr. The annual cost of filling out tax forms for the U.S. is estimated at $20 billion dollars annually. I therefore conclude that global funds for planting 12 million ha/yr are not a limiting factor. The limiting factor is the priorities of our society. Some people believe we have a moral obligation to make sure that future generations have an equal or even greater supply of wood than we have claimed for ouselves (Schulz 1993). However, planting trees today to benefit our children and grandchildren may not be a high priority for many societys in the world.
Take steps to increase the planting of trees for fuel and fiber. Set a global planting goal to increase plantations to 630 million ha by the year 2050 (250 million ha for industiral roundwood; 250 million ha for firewood in developing countries; 130 million ha for biomass-fuelwood in developed countries). Encourage afforestation of pasturelands. End tax subsidies for parents having more than one child. Just do it.
A Position of the Society of American Foresters. Adopted by the Council of the Society of American Foresters on May 2, 1984, and renewed on November 10, 1987, November 13, 1990, December 7, 1994 and December 5, 1994.
The relationship of human populations to forestland resources is a critical factor in achieving the full benefits of those resources. As human populations continue to increase substantially, increased demands of forestland resources will result.
The United States has the capacity to provide leadership in this global population challenge–as it has done in the conservation movement. Our legislative measures to ameliorate air and water pollution and toxic wastes and to protect endangered species and wildlands have established a world standard. Yet these measures treat only the symptoms of uncontrolled population growth. This primary conservation issue has yet to be seriously addressed by the nation.
Professional foresters are concerned about the destruction and degradation of habitat for both humans and wildlife. Mounting population pressures not only lower the quality of life for humans but also contribute to the extinction of plant and wildlife species. The parallels of current population trends to wildlife management principles are obvious–in some places people are overrunning their own habitat and that of other life forms and making natural-resource management ineffectual. The best science and technology we can devise will not extricate us from the absolute limitations of the carrying capacity of our environment.
The relationship of human populations to forestland resources is a critical factor in optimizing forest benefits. If human populations expand substantially in the future, considerable increases in the demands on forestland resources will occur. While recognizing that the much debated political aspects of population policy are peripheral to the expertise of professional forestland managers, we also recognize that the long-term effectiveness of forest management and conservation efforts depends on the resolution of this major domestic and global challenge. Therefore, the Society encourages efforts to place before the public scientific information on the dangers of unlimited population expansion and the land-management options that will have to be faced.
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Figure 1. The author’s projected decrease in the world’s forests in comparison to a projected increase in the world population (World Resources Institute 1992). Some estimate the world’s forests for 1990 at about 3.4 billion ha (FAO 1995).
Figure 2. The amount of firewood in storage for three hypothetical islands.
Figure 3. The mean annual increment (MAI) for the native woods on Island A, the exotic plantation on Island B (with no research), and for the exotic plantation on Island C (after 100 years of research).
Figure 4. The population growth curve for all three island and the respective year when the population cuts down part of the preserve.
Figure 5. Projected increases in pine plantations in comparison with the amount of natural hardwood stands (bottomland plus uplands) for the state of Alabama (USDA 1988).
Figure 6. The global increase in roundwood consumption from 1981 to 1991 indicates a steady increase in wood consumption from developing counties (FAO 1992).
Figure 7. The expected decrease in timberland in the United States and the expected increase in roundwood consumption (USFS 1989).
Figure 8. The trend in tree planting in the United States from 1980 to 1994 (Moulton et al. 1995).
Figure 9. A comparison of land uses (tree plantations vs. pastures) for six countries. Countries with more tree plantations than pastures include Japan and Sweden.
Figure 10. A comparison of the increase in tree plantations and pastures since 1955 (World Resources Institute 1986; 1992).