United States Department of Agriculture Guide to the Forest Service Ecological Systems International Institute of Tropical Forestry of Puerto Rico General Technical Report IITF-GTR-35 June 2009 Gary L. Miller and Ariel E. Lugo The Forest Service of the U.S. Department of Agriculture is dedicated to the principle of multiple use management of the Nation’s forest resources for sustained yields of wood, water, forage, wildlife, and recreation. Through forestry research, cooperation with the States and private forest owners, and management of the National Forests and national grasslands, it strives—as directed by Congress—to provide increasingly greater service to a growing Nation. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable sex, marital status, familial status, parental status, religion, sexual orientation genetic information, political beliefs, reprisal, or because all or part of an individual’s income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 720-2600 (voice and TDD).To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W. Washington, DC 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. Authors Gary L. Miller is a professor, University of North Carolina, Environmental Studies, One University Heights, Asheville, NC 28804-3299. Ariel E. Lugo is the Director of the U.S. Department of Agriculture, Forest Service, International Institute of Tropical Forestry, Jardín Botánico Sur, 1201 Ceiba Street, Río Piedras, PR 00926-1115. Abstract Miller, Gary L.; Lugo, Ariel E. 2009. Guide to the ecological systems of Puerto Rico. Gen. Tech. Rep. IITF-GTR-35. San Juan, PR: U.S. Department of Agriculture, Forest Service, International Institute of Tropical Forestry. 437 p. This guide is an introduction to the ecological systems of Puerto Rico. It covers the diversity of ecological systems in the island, their most common plant and animal species, and salient aspects of their structure and functioning. Terrestrial, wetland, coastal, and marine ecosystems are included, as well as agroforest and urban sys- tems. The discussion of the ecological systems of Puerto Rico is presented in the historical, cultural, and natural disturbance regime of the Island. In addition, we discuss the environmental infrastructure and organizations responsible for the conservation of Puerto Rico’s natural resources, and provide useful information to facilitate field visits to representative examples of the Island’s ecological systems. Keywords: Ecological systems, rain forests, dry forests, tropical forests, coral reefs, estuaries, mangroves, seagrasses, Puerto Rico. Preface This publication arose as a result of a series of field trips conducted in Puerto Rico by Gary L. Miller and Ariel E. Lugo with students on courses in tropical ecology at various Puerto Rican and U.S. colleges and universities. The field trips in many cases were preceded by semester-long lecture courses with field courses varying in length from a few days to 4 weeks. Through the years, a variety of handouts have been prepared describing many of the topics covered in this publication. The amount of literature centered on Puerto Rico and the Caribbean has grown tremen- dously in the last two decades. Because these courses were geared toward under- graduates, however, much of the technical literature was too voluminous and, in some cases, too technical for a lay audience. In response, this book was written to include a mixture of technical and applied information that a diverse reading audi- ence might find ecologically informative and generally interesting. It covers most of the important ecological systems, a selected group of species, and some of the important environmental issues confronting Puerto Rico and the Caribbean today. Although most of the technical publications and data sets cited were derived from studies conducted in Puerto Rico, much of what is generally described in terms of ecosystems and species is typical of most islands in the Caribbean. Clearly there is much variation from island to island in regard to size, soils, topography, altitude, rainfall, and accessibility. There is, however, considerable overlap in species and ecosystem presence. In addition, all of the Caribbean islands are experiencing simi- lar problems related to expanding human populations, providing environmentally based amenities, protecting species and habitats; environmental catastrophies such as hurricanes, landslides, and floods; and loss of their fisheries owing to overfish- ing. For these reasons, this guide is relevant throughout the Caribbean region. In addition, useful and practical information, such as the location of habitats for field trips, references to environmental agencies, field trip checklists, videotapes, maps, and guides to Puerto Rico has been provided in appendix 2. For those want- ing more technical information, many citations to recent technical literature are provided in each section. The material is meant to be used according to areas of interest, and for this reason, we allow some redundancy among sections. We hope this publication will provide a better fundamental knowledge of the environmental conditions of Puerto Rico and the Caribbean. Contents 1 Chapter 1: Overview of Puerto Rico 1 Introduction 4 Puerto Rico—Its History, Politics, and Economy 4 Early History 7 The Colonial Period 8 Steps Toward Autonomy 8 The American Period 12 Contemporary Puerto Rico 18 Physical and Climatic Zones of Puerto Rico 18 Geography 20 Climate 21 Hurricanes 23 Geology 25 Soils 27 Chapter 2: Flora and Fauna of Puerto Rico and the Caribbean 27 General Review of the Flora 33 Trees 36 General Review of the Fauna 52 Tree Frogs 55 Birds 58 Neotropical Migrants 63 Bats 67 Termites 70 Endangered Species 79 Chapter 3: Terrestrial Ecosystems 79 Subtropical Forest Life Zones of Puerto Rico 83 The Subtropical Dry Forest 94 The Subtropical Moist Forest 105 The Subtropical Wet Forest 113 The Subtropical Rain Forest 125 The Subtropical Lower Montane Wet Forest 132 The Subtropical Lower Montane Rain Forest 135 Agroecosystems 137 Typical Crops of the Tropics 157 Chapter 4: Freshwater Wetlands and Coastal Ecosystems 157 Wetlands Ecosystems 170 Wetlands Regulation 174 Coastal Ecosystems 174 Sandy Beach Habitat 188 Rocky Shoreline Habitat 195 Chapter 5: Estuarine Ecosystems 195 Mangrove Forests 200 Ecological Functions of Mangroves 205 Zonation of Mangrove Communities 207 Extent of Puerto Rico’s Mangroves 209 Stressors 212 Values of Mangroves 213 Riverine Estuaries 219 Chapter 6: Marine Ecosystems 219 Submerged Seagrasses 233 Coral Reefs 248 Keeping Your Keel Off Coral 264 Symbiosis 267 Coral Dieback 273 Chapter 7: Disturbances in Puerto Rico and the Caribbean 273 Hurricane Effects on Ecosystems 274 Terrestrial Effects 278 Marine Effects 282 High Rainfall, Drought, Landslides, and Fire Events 285 The Urban Forest Interface 291 Chapter 8: Environmental Organizations and Environmental Infrastructure 291 The El Yunque National Forest and the International Institute of Tropical Forestry 298 Puerto Rico’s Commonwealth Forests and Nature Reserves 304 Caribbean Islands National Wildlife Refuge 308 Other Environmental Organizations 310 Acknowledgments 310 Metric and English Conversion 311 Literature Cited 322 Further Reading 345 Appendix 1: Common and Scientific Names of Plant and Animal Species 363 Appendix 2: Visiting Puerto Rico 383 Appendix 3: Ecotourism 387 Appendix 4: Tools 404 Glossary 425 Index This page is intentionally left blank. Guide To The Ecological Systems Of Puerto Rico Chapter 1: Overview of Puerto Rico Introduction Puerto Rico offers a rich tapestry of environments in which to conduct field studies in tropical ecology. It has a mountain range oriented east-west with peaks as high as 1000 meters (4,000 feet). Its boundary on the north is the Atlantic Ocean and to 1 the south, the Caribbean Sea. The island is bathed by the westerly trade winds, which interact with the sea and mountains to produce an array of rainfall patterns and orographically induced habitat variation. Some areas in the mountains receive more than 5000 millimeters (200 inches) of rain annually. Other areas on the Caribbean rain shadow side receive as little as 254 millimeters (10 inches) in some years. In addition, the rainfall produces considerable runoff that results in many rivers on the island in all directions. The south side has fewer perennial rivers and is a lower energy coast line, thus affording greater stability to marine ecosystems such as coral reefs, mangrove swamps, and submerged seagrass beds. Because of its geographic position, half the year Puerto Rico is also exposed to major tropical storms. Hurricanes are one of the main ecological disturbances in Puerto Rico and all adjacent areas of the Caribbean, and have the potential of pro- ducing enormous instantaneous and long-term change in all ecosystems, terrestrial and marine. Pre-Columbian Puerto Rico had no coconut palms,2 no grapefruit or orange trees, no coffee groves, no mangoes, no flamboyán or African tulip trees with their beautiful flowers, and no sugarcane fields.