The trajectory of accumulating information about tropical deforestation exhibits a recognizable pattern. Throughout the 1980s as concern about the problem grew, the rate of publication also increased, from 8 publications in 1980 to 41 publications in 1989. Since 1990 the rate of publication has remained relatively constant, between 45 and 60 publications per year.
Half of all of the publications have come out since 1992. Almost one-third of the publications on tropical deforestation have no clear geographical referent; they discuss a particular aspect of the problem in an abstracted way or they undertake a global analysis of the problem. Slightly more than two-thirds of the studies have a clear geographical referent, and they are distributed unevenly across countries.
Table One outlines the geographical distribution of studies across the different regions containing tropical rain forests. It brings together data on the numbers of studies of deforestation processes in these regions with data on the extent of rain forests and the deforestation rate in these regions. Several patterns are apparent. First, one might expect that the numbers of studies should be distributed roughly in proportion to the extent of rain forests across nations. Those countries with large rain forests would be studied frequently while countries with small forests would be studied rarely. This pattern exists; the correlation coefficient between the two variables is .842 (p < .001). Although periodically analysts complain about an exclusive focus in the literature on events in the Brazilian Amazon (Carr, 2000), this pattern is not evident in the literature. If anything, using the area criterion, Brazil appears understudied. It contains 32% of the world’s tropical rain forests and has been the subject of 17% of the studies. For other patterns the reader might consult Appendix B which contains a listing of the number of studies and tropical forest areas for 73 countries.
Table 1. Where Have the Studies Been Done?: Numbers of Studies, Regional Forest Size, and Deforestation, 1970s - 2000
REGIONS |
PERCENTAGE OF STUDIES |
PERCENTAGE OF TROPICAL FORESTS, 1990 |
MEAN REGIONAL DEFORESTATION RATE (% per year), 1981-90 |
Central America |
17.15 |
4.30 |
2.19 |
South America |
32.02 |
48.19 |
.97 |
West Africa |
7.89 |
5.95 |
.85 |
Central Africa |
5.16 |
14.08 |
.57 |
East Africa |
7.28 |
8.61 |
.73 |
South Asia |
6.22 |
6.07 |
1.43 |
Southeast Asia |
23.22 |
12.71 |
1.40 |
Oceania |
1.06 |
.09 |
.20 |
Sources: For inventory of studies, this project; for extent of forest area and deforestation rate, FAO, 1993.
Analysts also tend to study places with the highest deforestation rates (correlation coefficient = .402, p < .01). This tendency probably accounts for the disproportionate numbers of deforestation studies carried out in Central America and Southeast Asia (see Table One). The particular concentrations of studies in Costa Rica (forest area = .08%, studies = 3.66%), Ecuador (forest area = .70%, studies = 5.50%) and the Philippines (forest area = .46, studies = 5.19%) seems partially explicable in these terms. From an information management point of view this pattern has the happy consequence of providing the most information about deforestation processes in those places that have had the highest rates of deforestation.
Other patterns in the data do not lead to so sanguine a conclusion. For rather obvious reasons researchers have not studied rain-forest regions plagued by civil unrest. For example, our search did not find any studies of deforestation trends or processes in any of the former Portuguese colonies in Africa (Angola, Guinea-Bissau, Mozambique). Each of these nations has experienced extensive civil unrest since 1970. In the Americas the relative paucity of deforestation studies in Colombia is surprising given its relatively high rates of deforestation, and the large concentrations of researchers studying deforestation in nearby countries (Ecuador, Panama, and Costa Rica). Civil unrest probably explains the lack of research.
Given the constraints faced by field researchers in these places, remote sensing studies of deforestation processes may have a particularly important role to play in these settings.
The research methods employed by students of deforestation processes have also changed during the last two decades. Table Two summarizes these changes. General studies drawing on secondary sources and first hand accounts by field researchers predominate in the early publications about the problem. The methodological patterns changed from the 1980s to the 1990s. Well funded remote sensing and survey based studies have increased in frequency while first hand accounts of deforestation processes have declined in number. The numbers of studies based exclusively on secondary sources have also declined somewhat although they remain at a high level, about 46% of the published research in the 1990s. Given the greater measurement precision attainable through remote sensing analyses, household surveys, and combinations of the two, the increased use of these methods is a positive development. The geographical distribution of remote sensing based studies is relatively broad. Only 27% of them concern Brazil; significant numbers of remote sensing studies of tropical deforestation have been carried out in Ecuador, Madagascar, and the Philippines.
Table 2. Tropical Deforestation Studies Categorized by Primary Information Source: Trends over Time
REMOTE SENSING |
SURVEY |
FIELD OBSERVATION |
SECONDARY SOURCE |
TOTALS | |
Pre-1980 Data |
7 8.0% |
7 8.0% |
34 38.6% |
40 45.5% |
88 100% |
1980s Data |
27 8.2% |
15 4.6% |
101 30.5% |
189 56.7% |
332 100% |
1990s Data |
47 16.7% |
42 14.9% |
55 19.5% |
132 46.8% |
276 100% |
Totals |
81 11.6% |
64 9.2% |
190 27.3% |
361 51.9% |
696 100% |
Chi-Square = 46.35, p < .001
Our survey of the tropical deforestation literature had two purposes: describe the knowledge base that has accumulated over the years and describe the patterns of causation which prevail in the literature. Tables Three and Four array the data on the causes of deforestation.
In effect we are using the Delphi method, questioning a panel of experts, to ascertain whether or not there are large regional differences in the attributed causes of deforestation and whether or not these attributed patterns of causation have changed over time. Because the conclusions outlined below rely on expert opinion rather than the systematic comparison of directly observed deforestation processes, the results need to be interpreted with caution. They are, for example, affected by the rate at which experts publish their work. The judgements of researchers who publish more will count more in this type of exercise than will the judgements of researchers who count less. By extension conditions in a frequently studied country like Ecuador will count more in characterizing regional tendencies than will conditions in a less studied country like Colombia.
Given the difficulty of doing the explicit comparative work referred to above which would produce more comparable cross-national and cross-continental results, the Delphi method used here may have some value.
Table 3. Regional Variations in Attributed Causes of Deforestation
Region | ||||||||
Causes* |
SE Asia |
South Asia |
East Africa |
Cent. Africa |
West Africa |
Cent. Amer. |
South Amer. |
Sum |
Log. |
80 37.7% |
12 5.7% |
7 3.3% |
6 2.8% |
12 5.7% |
32 15.1% |
58 27.4% |
212 100% |
Ranch. |
4 2.4% |
7 4.2% |
7 4.2% |
1 .6% |
4 2.4% |
57 33.9% |
88 52.4% |
168 100% |
Plant. |
33 25.0% |
6 4.5% |
8 6.1% |
3 2.3% |
9 6.8% |
25 18.9% |
46 34.8% |
132 100% |
Small. Agr. |
77 25.2% |
14 4.6% |
27 8.9% |
7 2.3% |
14 4.4% |
59 19.3% |
102 33.4% |
300 100% |
Fuelwood |
18 21.4% |
11 13.1% |
23 27.4% |
4 4.8% |
4 4.8% |
9 10.7% |
12 14.3% |
81 100% |
Roads |
19 13.4% |
2 1.4% |
3 2.1% |
1 .7% |
4 2.8% |
29 20.4% |
84 59.2% |
142 100% |
Pop. |
41 28.3% |
9 6.2% |
21 14.5% |
7 4.8% |
10 6.9% |
22 15.2% |
34 23.4% |
144 100% |
Colon. |
33 17.7% |
2 1.1% |
3 1.6% |
1 .5% |
3 1.6% |
43 23.1% |
100 53.8% |
185 100% |
Market Exp. |
28 23.0% |
4 3.3% |
11 9.0% |
3 2.5% |
4 3.3% |
27 22.1% |
44 36.1% |
121 100% |
Pub. Pol. |
54 24.8% |
8 3.7% |
16 7.3% |
3 1.4% |
5 2.3% |
41 18.8% |
90 41.3% |
217 100% |
Number of Studies |
128 22.3% |
27 4.7% |
48 8.4% |
22 3.8% |
25 4.4% |
106 18.5% |
207 36.1% |
563 100% |
* Log. = Logging, Ranch. = Ranching, Plant. = Plantation, Small. Agr. = Smallholder agriculture,
Pop. = Population Increase, Colon. = Colonization Programs, Market Exp. = Market Expansion,
Pub. Pol. = Public Policy.
Analysts have periodically observed that the causes of tropical deforestation vary dramatically by region (Rudel and Roper, 1996). Table Three explores this possibility by cross-tabulating the attributed causes of deforestation in a study by the region in which the study took place. To interpret the table visually, the reader should compare the row percentages for a particular cause with the overall row percentages at the base of the table. When these two percentages deviate significantly, then that particular cause for deforestation would have a differential impact across the regions, present as a primary cause of deforestation in some regions and absent as a cause in other regions.
Taken together, the literature indicates the disproportionate influence that loggers have had on deforestation processes in Southeast Asia. The arid and populous regions of East Africa and South Asia have been vulnerable to deforestation driven by demands for fuelwood. Population increase drives deforestation to a greater extent in Africa and Asia than it does in Latin America. Colonization programs, associated road building, and an expansion in cattle ranching have induced people to clear tropical forests in Latin America. Smallholder agriculture, plantations, market expansion, and public policy seem to operate with equal intensity as driving forces in all of the regions.
Table Four explores the degree to which the different forces driving tropical deforestation have changed over time. A number of driving forces appear to remain unchanged over time. Logging, plantation expansion, smallholder agriculture, road building, population increase, and demands for fuel wood are cited as frequently in the 1990s studies as they are in the pre- 1980s studies. Several factors, operative in Latin America, appear to have become less influential over time. When Brazil cut the subsidies for enterprises located in the Amazon basin in the late 1980s, the incentives to create or expand large, corporate cattle ranches declined, so the expansion of cattle ranches into the forest may have slowed (Browder, 1994). Similarly, the negative publicity and poor performance of government colonization projects led governments to scale back or abandon these programs in South America during the 1980s, so they no longer contribute to land clearing. Two factors associated with globalization appear to have grown in importance. More researchers in the 1990s cited the spatial expansion of markets through the growth in urban populations, improvements in transportation, and the search for raw materials in more remote settings as a cause of deforestation. The increased amounts of foreign debt which has resulted in structural adjustment agreements has led to a renewed emphasis on the expansion of export crops at the expense of the forest (Kaimowitz, Thiele, and Pacheco, 1999). It is of course difficult to know whether or not these changes in patterns of attribution represent real changes in the relative significance of causes or just changes in the salience of these factors in the researchers’ minds. More detailed work on region specific changes in the relative salience of the different causal factors may help answer this question.
Table 4. Trends over Time in Attributed Causes of Deforestation
Pre-1980s Data |
1980s Data |
1990s Data |
Sum | |
Logging |
41 13.1% |
149 47.6% |
123 39.3% |
313 100% |
Ranching |
36 15.6% |
123 53.2% |
72 31.2% |
231 100% |
Plantations |
28 15.6% |
83 46.4% |
68 38.0% |
179 100% |
Smallholder Agriculture |
56 14.0% |
193 48.4% |
150 37.6% |
399 100% |
Fuelwood |
11 7.9% |
77 55.0% |
52 37.1% |
140 100% |
Roads |
27 15.6% |
80 46.2% |
66 38.2% |
173 100% |
Market Expansion |
17 9.6% |
79 44.6% |
81 45.8% |
177 100% |
Population |
27 12.6% |
105 48.8% |
83 38.6% |
215 100% |
Debt |
0 0% |
28 60.9% |
18 39.1% |
46 100% |
Colonization |
37 16.4% |
122 54.0% |
67 29.6% |
226 100% |
Number of Studies |
88 12.7% |
335 48.5% |
268 38.8% |
691 100% |
