2010 THE THREAT TO BIODIVERSITY AND ECOSYSTEM FUNCTION OF PROPOSED HYDROELECTRIC DAMS IN THE LA AMISTAD WORLD HERITAGE SITE, PANAMA AND COSTA RICA. Dr. William O. McLarney Lic. Maribel Mafla H Lic. Ana María Arias Lic. Danielle Bouchonnet 0 THE THREAT TO BIODIVERSITY AND ECOSYSTEM FUNCTION IN THE LA AMISTAD WORLD HERITAGE SITE, PANAMA AND COSTA RICA, FROM PROPOSED HYDROELECTRIC DAMS A follow-up to McLarney and Mafla (2007): Probable Effects on Aquatic Biodiversity and Ecosystem Function of Four Proposed Hydroelectric Dams in the Changuinola/Teribe Watershed, Bocas del Toro, Panama, with Emphasis on Effects Within the La Amistad World Heritage Site With consideration also of La Amistad/Costa Rica and the Pacific Slope of La Amistad. Dr. William O. McLarney Lic. Maribel Mafla H. Lic. Ana Maria Arias Lic. Danielle Bouchonnet Programa de Biomonitoreo Asociación ANAI Contact Information: Asociación ANAI (Costa Rica): ANAI, Inc. (United States): Apdo. 170-2070 1120 Meadows Rd. Sabanilla de Montes de Oca Franklin, North Carolina 28734 Costa Rica, C.A. USA Phone: (506) 2224-3570 Phone/fax: (828) 524-8369 (506) 2756-8120 E-mail: [email protected] Fax: (506) 2253-7524 E-mail: [email protected] [email protected] Respectfully submitted to: UNESCO World Heritage Committee February, 2010 1 Table of Contents EXECUTIVE SUMMARY 5 RESUMEN EJECUTIVO 8 INTRODUCTION 11 DAMS AS BARRIERS, AND THE IMPORTANCE OF DIADROMY 13 EFFECTS OF DAMS ON DIADROMOUS ANIMALS IN MESOAMERICA AND THE CARIBBEAN 17 EVENTS SINCE 2008 19 1. Social, Political and Legal Events: 19 Panama-Atlantic slope: 19 Panama-Pacific slope: 19 Costa Rica-Pacific slope: 20 Costa Rica-Atlantic slope: 20 2. Biological Investigations: 21 Panama: 21 Costa Rica – Pacific slope: 25 Costa Rica – Atlantic slope: 26 Darwin Initiative: 26 THE LA AMISTAD AREA AND ITS WATERSHEDS 28 THE LA AMISTAD AREA 28 FLUVIAL SYSTEMS OF LA AMISTAD, WITH COMMENTS ON PLANNED DAMS 30 Atlantic slope – Panama: 30 Changuinola/Teribe watershed 30 Atlantic slope – Costa Rica: 31 Sixaola/Telire watershed 32 Estrella watershed 33 Banano watershed 33 Matina watershed 34 Pacific slope – Costa Rica: 34 Grande de Terraba Watershed 34 Pacific slope – Panama: 35 Chiriqui Viejo, Piedras/Chico and Chiriqui watersheds 35 Conclusion: 36 THE AQUATIC FAUNA OF LA AMISTAD 37 FISH 37 Introduction and Overview: 37 ATLANTIC SLOPE SPECIES: 39 Family Anguillidae 39 Anguilla rostrata 39 Family Atherinidae 39 Atherinella chagresi 39 Family Gobiesocidae 40 Gobiesox nudus 40 Family Gerreidae 41 Eugerres plumieri 41 2 Family Haemulidae 41 Pomadasys crocro 41 Family Mugilidae 42 Agonostomus monticola 42 Joturus pichardi 43 Family Gobiidae 44 Awaous banana 44 Sicydium spp. 45 Family Eleotridae 46 Gobiomorus dormitor 46 OTHER FISHES OF CONCERN: 48 Potamodromous species: 48 Cryptic diadromous species: 48 Euryhaline facultative wanderers: 49 “New” species: 49 Pacific slope diadromous species: 50 MACROINVERTEBRATES 51 BENTHOS: 51 SHRIMPS: 53 Overview: 53 ATYIDAE – ATLANTIC SLOPE: 55 Atya inocous 55 Atya scabra 55 Jonga serrei 55 Micratya poeyi 55 Potimirim glabra, Potimirim mexicana, and Potimirim potimirim 55 PALAEMONIDAE – ATLANTIC SLOPE: 56 Macrobrachium acanthurus 56 Macrobrachium carcinus 56 Macrobrachium crenulatum 56 Macrobrachium heterochirus 56 Macrobrachium olfersi 57 ATYIDAE – PACIFIC SLOPE: 57 PALAEMONIDAE – PACIFIC SLOPE: 57 SUMMARY: 58 SECONDARY EFFECTS OF SPECIES EXTIRPATIONS OR DRASTIC POPULATION DECLINES ABOVE DAMS 59 Predator – prey relationships: 59 Frugivores: 59 Omnivores, herbivores and detritivores: 60 General considerations: 60 Effects in high altitude streams: 60 1. Sediment dynamics: 62 2. Breakdown of allochthonous vegetable matter: 63 3 3. Water and substrate chemistry: 64 4. Algal biomass and diversity: 65 5. Structure of the benthic macroinvertebrate assemblage: 66 Conclusion: 67 UNIQUE CHARACTER OF LA AMISTAD FLUVIAL ECOSYSTEMS AND THEIR RELATION TO OTHER ECOSYSTEMS 68 Importance of high altitude streams: 68 Uniqueness of La Amistad fluvial ecosystems: 70 Terrestrial systems within the World Heritage Site: 72 Downstream effects of natural barriers: 73 On site and downstream effects of dam/reservoir complexes: 74 Overview and reservoir effects: 74 Downstream effects: 76 Dewatering 77 Flow rate 77 Sediment transport 77 Temperature regimes 78 Changes in water chemistry 79 MITIGATION 80 Fish passage strategies: 80 Artificial rearing of migratory species: 82 The “landlocking” phenomenon: 83 Downstream mitigation: 84 Mitigation at the regional scale: 84 Conclusion: 85 RECOMMENDATIONS 87 ACKNOWLEDGEMENTS 89 REFERENCES CITED 90 APPENDIX I. TABLES 112-116 APPENDIX II. MAPS 117-123 4 EXECUTIVE SUMMARY In this paper we expand and update our previous report “Probable Effects on Aquatic Biodiversity and Ecosystem Function of Four Proposed Hydroelectric Dams in the Changuinola/Teribe Watershed, Bocas del Toro, Panama, with Emphasis on Effects Within the La Amistad World Heritage Site”, taking into account events occurring since that report was presented in February, 2008 and expanding coverage to include all of the La Amistad World Heritage Site watersheds in both countries and on both sides of the Continental Divide. This is necessary because it has become increasingly apparent that, chiefly as a consequence of dam proposals and in direct contravention of one of the stated purposes for declaring the La Amistad National Parks, all of the major watersheds within the World Heritage Site are threatened with multiple species extirpations and consequent secondary effects which stand to grossly alter the character of ecosystems within the Site and the surrounding protected areas and indigenous territories making up the La Amistad Biosphere Reserve. For the sake of convenience, in much of the discussion we divide the La Amistad region into 4 sectors – Costa Rica and Panama, Atlantic and Pacific slopes. While this report focuses on biological events and predictions, we must take note of the numerous protests against dam plans and associated development which have occurred in all 4 sectors, based not only on environmental issues, but also reflecting valid socio-cultural, indigenous rights and local economic concerns. Of particular concern are open pit mining plans being developed in Bribri territory on the very periphery of the World Heritage Site on the Atlantic slope of Costa Rica, and which are perceived as related to nearby dam sites. Results of several important biological investigations in the La Amistad area have been published since our last report. These include inventories of fish and macroinvertebrates carried out by University of Costa Rica biologists and sponsored by ICE in the Grande de Terraba River drainage on the Paciflc slope of Costa Rica, advances in Asociacion ANAI’s continuing biomonitoring investigations on the Atlantic slope of that country, and an ongoing binational Darwin Initiative inventory focusing on the World Heritage Site, which has already reported numerous new country records and discovered 31 species of animals and plants new to science. However, perhaps the most immediately significant new investigation is a series of inventories undertaken by the Smithsonian Tropical Research Institute (STRI) in the portion of the Changuinola River watershed which would be directly affected by the CHAN-75 and CHAN-140 dams. Along with important new species records, the STRI report confirms the ANAI biomonitoring team’s assertion (based on monitoring in the Atlantic slope watersheds of Costa Rica and non-quantitative surveys in the Changuinola/Teribe watershed of Panama) of overwhelming dominance by diadromous migratory fish and shrimp in streams at middle and upper elevations on the Atlantic slope of the La Amistad area. Unfortunately, the Executive Summary of the extremely long (total 1,081 pages) STRI report attempts to serve public relations functions by underplaying the significance of diadromy and glossing over problems and limitations which are acknowledged in the full text. This tendency is extended and exacerbated in the recently published mitigation proposal by the engineering firm AES Changuinola and the consulting firm MWH which does however constitute an important new bibliographic resource. Descriptive sections of the present ANAI report place the rivers which arise within the La Amistad World Heritage Site in a geographic context of the ca. 10,000 sq. km. La Amistad Biosphere Reserve, and review the fish and macroinvertebrate taxa known from these watersheds, with emphasis on diadromous species known to occur within the World Heritage Site. For each of the 4 sectors of the La Amistad area we analyze all publicly available information on proposed dams and relate it to the threat of species extirpation and related ecological consequences. For the Pacific slope of Panama, we note that all access by diadromous species to streams within the World Heritage Site is already blocked by existing or nearly completed dams, leading to a hypothesis of 5 total or near-total species extirpation. On the Atlantic slope of Panama, the only significant change since 2007 is progress toward completion and closure of the CHAN-75 and Bonyic Dams. We report on proposals for 8 dams on the Atlantic slope of La Amistad/Costa Rica, and plans for one large and several smaller dams on the Pacific slope of that country. We conclude that if all presently proposed dams are constructed, 67% of the total watershed area of the La Amistad World Heritage Site will become inaccessible to diadromous and other upstream/downstream migratory