TROPINET, Vol. 12, No. 2, June 2001


Ten Years After: Puerto Rico As A Model For Understanding Tropical Reforestation

Jess K. Zimmerman, Director, Institute for Tropical Ecosystem Studies, University of Puerto Rico, Río Piedras Campus, Río Piedras, Puerto Rico

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Landsat image from the mid-1980s showing eastern Puerto Rico. The coastline and dark areas of water appear on the right side of the image (Roosevelt Roads Naval Base is also apparent). Darker areas on land represent forest cover. The largest area represents the Luquillo Experimental Forest, of which only the central and most elevated areas represent primary forest. The flanks of the Luquillo Mountains and outlying forest patches represent secondary forest less than fifty years old with a variety of land uses dominated by coffee cultivation and pasture.


As I approach my tenth anniversary of working in Puerto Rico, I take this opportunity to consider the research that my colleagues and I have done on the history of the forests in Puerto Rico. Shortly after arriving at the University of Puerto Rico, T. Mitchell Aide and I began a series of studies that took advantage of the five-fold increase in forest cover in Puerto Rico. The increase in forest cover, from a low of about 7% in the late 1940s, to 35% in 19851, was the result of dramatic socioeconomic changes that were initiated in the late 1940s that led to the abandonment of marginal agricultural lands2. We presented this to our funding agencies as an opportunity to treat Puerto Rico as a "laboratory" in which to study the future condition of tropical forests. The unstated assumption was that if the economic miracle in Puerto Rico that led to the "forest transition"2 could be repeated elsewhere, then we could use Puerto Rico to predict the future status of the worlds tropical forests. In this essay, I address two questions: (1) What are the basic lessons of our research, and (2) Is the Puerto Rican model valuable for predicting the future of tropical forests worldwide?

Before addressing these questions, however, we need to put the changes in forest cover in Puerto Rico in context. The dramatic increase in forest cover in Puerto Rico is not unprecedented. For example in New England, forest cover increased from 25-50% from the mid-1800s to 65-90% by the late 20th century3 and similar examples can be found throughout the eastern U.S., Europe, and temperate Asia. In the tropics, forest cover has increased in other Antillean islands, and in Taiwan and Malaysia. Each of these "forest transitions" was associated with abandonment of marginal agricultural lands and immigration to urban areas, and often, by an increase in industrial production2. In Puerto Rico, the abandonment of agriculture and increased forest cover was further promoted by the ability of residents of Puerto Rico to immigrate to the U.S.

What have we learned from our research on secondary forests in Puerto Rico? We began with a simple approach: increases in forest biomass and diversity should differ among major agricultural practices with the rate of increase in both biomass and forest diversity rising in the order pasture < sugar cane < shade coffee. We predicted that shade coffee, because it has a canopy that would encourage dispersers, would promote the establishment of a diverse forest while pasture grasses are a persistent crop that would impede tree establishment.

Figure 1. Sweeping changes in forest species composition caused by effects of past land use in the Luquillo Experimental Forest, Puerto Rico7. Areas of abandoned coffee and pastures (40 60 years old) were compared to forest that had been selectively logged but never cut-over ("Forest"). Forest stands of each land use type were sampled at three sites: Bisley ("BS"), El Verde ("EV"), and Cubuy ("CB").

Forest recovering from sugar cane would exhibit an intermediate rate of recovery because it did not have a canopy to promote tree establishment, but it is not a persistent crop. To test this idea, we would use chronosequences of the different land use types to estimate potential changes in forest biomass and diversity. This simple approach failed because all shade coffee was abandoned essentially at the same time2 and there was largely no direct regeneration from cane, rather, cane fields were converted to pastures before they were abandoned4. Also, comparisons were confounded by correlations between land use and elevation5. Pasture chronosequences were easy to develop and revealed that forests could recover quickly, often achieving high biomass and levels of diversity within 30-50 years6. Also, comparison of equal-aged forests with different land use histories were possible and showed remarkable differences in species composition (Fig. 1)7. Comparisons of abandoned coffee and pastures revealed no differences in forest diversity7 or slightly reduced diversity in abandoned coffee8, contrary to our predictions. In summary, we found that, once abandoned, forests can recover in former agricultural lands in Puerto Rico, but these forests will exhibit strong legacies of past land use, reflected in variation in species composition among forest stands.

One of the lessons from New England was that human disturbance caused increased forest heterogeneity at the local scale (field to field) but increased homogeneity at the regional scale (e.g., township to township) 9. This is caused by legacies of specific agricultural practices (crop, frequency of plowing, etc.) at local scales but conversion to a generalized flora at regional levels as a result of human disturbance and a relatively short recovery time. We cannot complete the same analysis for Puerto Rico because we know little of the composition of undisturbed forest (except in special cases5,7), but it is clear that there are strong legacies of past land use that often produce forests of similar composition in areas with vastly different climates and geological substrates5,6,7,8. Perhaps different from New England, Puerto Rican secondary forests often include non-native species, particularly Spathodea campanulata6. Thus, in a broad sense, the forest transition in Puerto Rico produced the same pattern of variation of forest composition as observed in New England: high heterogeneity in forest composition at the local scale and a relatively homogeneous flora at the regional level. Thus, we would predict that, if other tropical countries experience the same forest transition as Puerto Rico, the structure of the variation in forest composition would be similar.

What is the likelihood that other tropical countries will experience the forest transition that Puerto Rico and other areas have? Increased globalization of the worlds economy and the lowering of trade barriers offers the hope that many tropical countries will be able to attain a level of affluence similar to that enjoyed by Puerto Rico. However, there may be a limit to which these economic advances can be achieved. A recent article spells out the socioeconomic correlates of the forest transition in Puerto Rico2: outmigration of small landholders from upland, coffee-growing regions to urban areas in Puerto Rico and the U.S. However, this tells only half of the story. Another important correlate in Puerto Rico is the conversion of prime agricultural lands in the lowland to urbanizations and a strong reliance on food imports10. Food imports increased 18-fold from 1950-1980 in Puerto Rico and similar patterns of land use change and increased reliance on food imports have been noted in Japan, South Korea, and Taiwan. Expanding upon the patterns in Asia, Lester Brown asked, "Who will feed China?"11.

Thus, the forest transition often comes at the expense of agricultural independence and there must be a limit to which the economic miracle of Puerto Rico can be repeated elsewhere in the tropics. It may be possible to achieve the forest transition in certain areas (e.g., the Andes), but as a general rule I doubt this can be achieved throughout the tropics unless we resolve the issue of where the food will come from to support the growing human population. Thus, as interesting as the situation is in Puerto Rico and while it may have application to some areas of the tropics, the economic realities of the forest transition must limit its generality.

Literature Cited

  1. Birdsey, R.A., and P. Weaver. 1987. Forest area trends in Puerto Rico. USDA Forest Service. Research Note #SO-331.
  2. Rudel, T.K., M. Perez-Lugo, and H. Zichal. 2000. When fields revert to forest: Development and spontaneous reforestation in post-war Puerto Rico. Professional Geographer 52:386-397.
  3. Foster, D.R. 2000. Conservation lessons & challenges from ecological history. Forest History Today Fall 2000 p. 3-12.
  4. Thomlinson, J.R., M.I. Serrano, T. del M. López, T.M. Aide, and J.K. Zimmerman. 1996. Landuse dynamics in a post-agricultural Puerto Rican landscape (1936-1988). Biotropica: 525-536.
  5. Pascarella, J.B., T.M. Aide, M.I. Serrano, and J.K. Zimmerman. 2000. Land use history and forest regeneration in the Cayey Mountains, Puerto Rico. Ecosystems 3:217-228.
  6. Aide, T.M., J.K. Zimmerman, J. Pascarella, L. Rivera, and H. Marcano-Vega. 2000. Forest regeneration in a chronosequence of tropical abandoned pastures: implications for restoration ecology. Restoration Ecology 8:328-338.
  7. Zimmerman, J.K., Aide, T.M., L.J. Herrera, M.A. Rosario, M.I. Serrano. 1995. Effects of land management and a recent hurricane on forest structure and composition in the Luquillo Experimental Forest, Puerto Rico. Forest Ecology and Management 77:65-76.
  8. Rivera, L.W., and T.M. Aide. 1998. Forest recovery in the karst region of Puerto Rico. Forest Ecology and Management 108:63-75.
  9. Foster, D.R., G. Motzkin, and B. Slater. 1998. Land-use history as long-term broad-scale disturbance: Regional forest dynamics in central New England. Ecosystems 1:96-119.
  10. López, T. del M, T.M. Aide, and J.R. Thomlinson. 2001. Urban expansion and the loss of prime agricultural lands in Puerto Rico. Ambio 30:49 54.
  11. Brown, L.R. 1995. Who will feed China? W.W. Norton & Co., New York, NY.




People and Forests: Communities, Institutions, and Governance. Edited by Clark C. Gibson, Margaret A. McKean, and Elinor Ostrom. 2000. MIT Press. 274 pp.

Review by Dr. Robert Buschbacher, Visiting Professor, University of Florida, Gainesville, FL, <>.

This book is an initial progress report for a long-term, multi-disciplinary, multi-country research effort aimed at understanding the interaction between local communities and forest resources. It is based on the International Forestry Resources and Institutions (IFRI) method, a research protocol developed and implemented by the Workshop in Political Theory and Policy Analysis, and by the Center for the Study of Institutions, Populations and Environmental Change, both at Indiana University.

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This book is a helpful antidote to those who promote simplistic, univariate explanations for the degradation of forest resources. Population pressure, accessibility, income alternatives, local control, and strong central governments have all been offered as the critical factor, but no one factor operates in isolation from many others. That is the basis of the IFRI method, which combines systematic sampling of forest structure and composition with data on use of forest products, community demographics, geographic variables, social relations among user groups, institutional and administrative arrangements, etc.

The researchers are applying this framework in an ambitious program of comparisons over time and across a large number of sites in many countries. There is little innovation here in terms of biological analysis; routine biological data are collected in order to systematically characterize forest status. The goal is to explain, from a social science perspective, why some forests are more degraded than others. More specifically, the books focus is on rural communities and the nature and capacity of community institutions to govern the use of forest resources. Other key determinants of forest use, such as economics and the effectiveness of governments, are recognized but not analyzed; they are treated as external variables which affect the communitys interest and capacity to manage the forest.

The books best chapter is the concluding one, in which the volumes three editors synthesize findings by elaborating a set of 12 variables -- some related to the characteristics of the resource and some to the characteristics of the users -- which affect the costs and benefits for a community to manage its forest resources. This framework helps to explain, for example, why placing control of a forest resource in the hands of a community may lead to good management in some cases but not others: factors such as degree of trust and organizational experience within the community, plus how readily the forest can be physically monitored and how evident changes in forest condition are to the community, are all critical.

Since the work is at a preliminary stage, the case studies, from a wide variety of developing country settings, each illustrate how a small number of these variables affect communities management of forest resources. For example, Varugheses study from the middle hills of Nepal shows that forest condition is unrelated to human population growth or density, while it is strongly related to the degree of collective activity (existence of entry and harvest rules, forest monitoring). The study does not yet elucidate, however, why some communities are more active than others. Other chapters look at the relationship between group size and the likelihood of successful collective action (India); analyze how forest governance, monitoring and community demand affect the spatial variability of Shorea populations (Nepal); consider the effects of tenure security and level of rule enforcement on forest condition (Uganda); look at how indigenous communities relationship with the forest changes upon introduction of market demand for timber (Bolivia); and analyze different internal interest groups to understand why a well-organized community has not developed forest management rules (Ecuador).

People and Forests provides an in-depth theoretical analysis, backed up by several preliminary case studies, of how and why communities develop governance structures to manage forest resources that they use, and whether this governance is effective.




Society for Conservation Biology 15th Annual Meeting. Theme: Ecological Lessons from Islands. 29 July 1 August 2001, Hilo, Hawaii USA. The scientific program will consist of a plenary address by Sir Robert May, 7 symposia, approximately 300 contributed oral presentations, two evening poster sessions, and a variety of workshops and discussions. The meeting is co-hosted by the Pacific Island Ecosystems Research Center (PIERC) of USGS Biological Resources, the University of Hawaii, and Hawaii's Secretariat for Conservation Biology. For information visit the website at << >>.

Ecological Society of America, 86th Annual meeting. Theme: Keeping All The Parts: Preserving, Restoring, and Sustaining Complex Ecosystems. 5-10 August 2001, Madison, Wisconsin USA. Information is available at <<>>.

Botanical Society of America: Botany 2001: Plants and People. 12-16 August 2001. Albuquerque Convention Center, Albuquerque, N.M. Participating societies include the American Bryological and Lichenological Society, American Fern Society, American Society of Plant Taxonomists, Botanical Society of America, International Organization of Plant Biosystematists. Information can be found at <<>>.

28th Annual Natural Areas Conference, 3 6 October, 2001. Cape Canaveral, Florida. The theme of the conference is "2001: A Spatial Odyssey Searching for a Natural Balance." Symposia, contributed papers, poster sessions, and field trips will attempt to explore how conservation, technology, and society can work together to balance the impacts of human activities on natural areas of the world. Scholarships are available to assist several international guests in attending this meeting. Scholarship applications are due by 1 August 2001. For more information, go to: <<>>.

"The roles of experimental biology in the protection of biodiversity and the control of exotic species". 11-13 September 2001, sponsored by The University of California Los Angeles, Institute of the Environment and the International Commission on Comparative Physiology of the International Union of Physiological Sciences. For more information, see the conference website at <<>>.

"Manipulating insect herbivory in biodiversity-ecosystem function experiments." 22-26 September 2001 Jena, Germany. Most terrestrial biodiversity-ecosystem function studies have so far concentrated on manipulating plant communities to study ecosystem processes. Herbivorous insects have been largely ignored, mainly for practical reasons. The proposed workshop at the University of Jena intends to address this discrepancy. The aim of this workshop is to provide a forum for discussing how existing knowledge on insect herbivory can be used in future studies on the functional role of biodiversity. The workshop will be limited to about 30 participants to allow intensive discussions. For further information, go to or contact Wolfgang Weisser <>>.

Local to Global:Tropical Conservation from the New England Region. 27 October 2001. Sponsored by the Center for Tropical Ecology and Conservation (CTEC) based out of Antioch New England Graduate School. The three sessions cover 1) environmental education in the tropics, 2) tropical ecology and conservation research, and 3) socioeconomic dimensions of tropical conservation. Paper and poster abstracts should be submitted by 6 August 2001. The Center is a new organization promoting education and research in tropical biology, conservation and the sustainable use of tropical ecosystems. The symposium will provide a foundation for developing relationships with individuals in the New England region who are active in tropical ecology and conservation efforts. Please contact us for more information: Beth Kaplin, Ph.D., Director, CTEC, Professor, Environmental Studies, Antioch New England Graduate School, 40 Avon St., Keene, NH 03431, (603) 357-3122 x238, <>, or see our web site at <<>>.

7th Annual World Wilderness Congress. 2-8 November 2001, Port Elizabeth, South Africa. For general information on the WWC7, visit their web-site at << >>.

14th Biennial Conference on the Biology of Marine Mammals. 28 28 November 3 December 2001, Vancouver, British Columbia Canada. Sponsored by The Society for Marine Mammalogy. The Vancouver Aquarium Marine Science Centre is hosting this international event. Current research on whales, dolphins, seals, sea lions, and other marine mammals will be showcased through spoken and poster presentations. Special events, video evenings, and vendor exhibits are planned as well. For information, visit <<>>.


Working Forests in the Tropics: Conservation through Sustainable Management. 24-26 February 2002 Gainesville, Florida, on the University of Florida campus. Tropical forests sustain a wealth of biodiversity, provide a wide range of ecosystem services and products, and support livelihoods for millions of people. Since less than ten percent of the world's tropical forests are likely to be preserved as legally protected areas, conservation of the remaining ninety percent will depend on the ability of stakeholders to make the products and services in these working forests provide appear competitive with alternative land use options. This conference will focus on what needs to be done to make this happen. For more information, registration and abstract submission visit the conference website at <<>>.


The Peregrine Fund works to conserve birds of prey and their habitats worldwide. We seek applicants for the position of Neotropical Program Director. The successful applicant will provide direction and oversight for The Peregrine Fund's programs throughout Latin America and the Caribbean, and coordination with The Peregrine Fund's other international and national (U.S.) programs. Applicants should have an advanced degree in a relevant field, proven management abilities, experience in fundraising, fluency in Spanish and English, and a willingness to live in Panama and travel internationally.

Send cover letter, resume and references as soon as possible to: International Programs Director, The Peregrine Fund, 566 West Flying Hawk Lane, Boise, ID 83709, U.S.A.

The School for Field Studies, Center for Sustainable Development Studies located in Atenas, Costa Rica, seeks an applied tropical ecologist for a resident faculty position. The successful applicant will teach U.S. university students about critical environmental issues, participate in developing and implementing an international curriculum at the Center for Sustainable Development Studies, and oversee faculty-designed student research projects. This position is the lead faculty for the course Tropical Ecology and Sustainable Development. Applicants should have a scientifically relevant Ph.D. (pref.) or Masters, applied/field research and university-level teaching experience in Applied Tropical Ecology, Agroecology, or Conserving Biodiversity, and fluency in English and Spanish (program delivered in English). To Apply: send CV and cover letter outlining relevant experiences to: Job Reference 1162 The School for Field Studies, 16 Broadway, Beverly MA 01915, USA; Fax: (978) 927-5127; E-mail: <>. For more information, please access our web page at: <<>>. EOE.


The U.S. Geological Survey of the Department of the Interior is presenting

a series of workshops pertaining to mapping, vegetation, photo-interpretation, remote sensing and Geographical Information Systems. The workshops are part of an effort to exchange information and provide access to spatial technologies developed at the center for natural resource survey. No previous experience is assumed. The three-day workshops are available to the general public, educators, state and federal agencies. Workshop participation by the international community is also greatly encouraged. Workshops will be held at the National Wetland Research Center and Mid-Continent Mapping Center, in cooperation with the University of Louisiana at Lafayette, in Lafayette, LA. CONTACT: <pat_o'>, website: <<>>.

17-18 July: Metadata for Geospatial Data

14-16 August: Introduction to Desktop GIS (ArcView) for Natural Resources

18-20 September: Introduction to GPS for Natural Resources

24-26 October: Introduction to Wetland Remote Sensing and Mapping

29-31 October: Advanced Wetland Photo-Interpretation

4-6 December: Introduction to Desktop GIS (ArcView) for Natural Resources

Multivariate Analysis of Ecological Data, to be held late January, 2002. This course is focused on application of ordination methods (PCA, DCA, RDA, CCA, PCoA) to visualize ecological datasets and to test multivariate statistical hypotheses related to such data. Additional topics covered in this course include clustering methods, TWINSPAN, and modern regression methods (generalized linear and generalized additive models). Participants are provided with sufficient time to work with their own research data. Detailed information can be found on the web page at: <<>>.


The Biosphere-Atmosphere Stable Isotope Network (BASIN) is pleased to announce a Travel Grants program to promote education and awareness of new stable isotope technologies and methodologies applied to biosphere-atmosphere exchange research. BASIN is soliciting applications from graduate students and young scientists to visit BASIN member study sites and laboratories within the U.S. Detailed information about BASIN and participating U.S. study sites can be found at: <<>>. Applicants must be enrolled M.S./Ph.D. students at an accredited institution or have a post-doctoral/research associate appointment at a university, government, or other research facility. Applications and inquiries should be sent to Diane Pataki, GCTE Focus 1 Science Officer, (801) 581-3545, <>. BASIN is a research network of the Global Change and Terrestrial Ecosystems (GCTE) core project of the International Geosphere-Biosphere Programme (IGBP).


(if you are interested in reviewing one of these books for Tropinet, please contact the editor at <>.)

Dorr, Laurence J., Basil Stergios, Alan R. Smith, and Nidia L. Cella A. 2000. Catalogue of the Vascular Plants of Guaramacal National Park, Portuguesa and Trujillo States, Venezuela. Contributions from the United States National Herbarium, Vol 40:1-155. Department of Botany, National Museum of Natural History, Washington, D. C. 2000.

Benzing, David H. 2000. Bromeliaceae: Profile of an Adaptive Radiation. Cambridge University Press, New York.

Lee, Julian C. 2000. A Field Guide to the Amphibians and Reptiles of the Maya World. Cornell University Press, Ithaca, NY.

Hall, Charles A. S. 2000. Quantifying Sustainable Development: The Future of Tropical Economies. Academic Press, San Diego.

Bowman, D. M. J. S. 2000. Australian Rainforests: Islands of Green in a Land of Fire. Cambridge University Press, New York.

Simmons, Nancy B. and Robert S. Voss. 1998. The Mammals of Paracou, French Guiana: A Neotropical Lowland Rainforest Fauna. Part 1. Bats. Bulletin of the American Museum of Natural History Number 237. American Museum of Natural History, New York.


NeoCons is a new, free electronic regional bulletin for Austral and Neotropical America.published by the Society for Conservation Biology, an international professional organization dedicated to promoting the scientific study of the phenomena that affect the maintenance, loss, and restoration of biological diversity ( The bulletin free of cost to all interested individuals, regardless of whether they reside or not in the region or they are or not members of SCB. The purpose of NeoCons is to facilitate information exchange in order to help strengthen the discipline of conservation biology in Austral and Neotropical America. NeoCons is published every two months and has two main sections. The first includes the table of contents of each issue of Conservation Biology in Spanish, while the second is a compilation of information items relevant to the practice of conservation biology. Contributions to NeoCons can be made in Spanish, English, Portuguese, and French. Instructions for subscribing and other details (in Spanish, Portuguese, French, and English) can be found at the website <<>>

InfoNatura is a new on-line resources for conservation information on all the birds and mammals of Latin America and the Caribbean - more than 5,500 common, rare, and endangered species in 44 countries and territories. InfoNatura is a product of the Association for Biodiversity Information in collaboration with Conservation Data Centers in 12 Latin American and Caribbean countries. This interactive site permits you to search our database for information on individual species, taxonomic groups, countries and conservation status, including the global conservation status ranks assigned by the Natural Heritage Network, the Red List category assigned to each species by the IUCN's (World Conservation Union) Species Survival Commission. Data also includes the protection status granted each species under the Convention on International Trade in Endangered Species (CITES). InfoNatura provides taxonomic data (including scientific and common names in English, Spanish and Portuguese), conservation status, references and national distribution information for each species included in the database. InfoNatura is available at: <<>>.

Ecosistemas is a fully electronic, free access and Spanish written popular science magazine in the fields of Ecology and Environmental Sciences, edited by the Spanish Association for Terrestrial Ecology. It is sited at <<>> (then click on Ecosistemas). All papers are reviewed and edited by profesional ecologists. Published material can be downloaded in two formats (Word and .pdf). Publishable material and informations to be posted are welcome as well. To submit, click on "Contacte con nosotros" (Contact us) for instructions to authors. Any material will be revised and edited prior to publication.