Distribution of Bird Diversity in a Vulnerable Neotropical Landscape

Abstract

Recent withdrawal of the U.S. military from the Republic of Panama has exposed 64,000 ha of lowland forest in the former Canal Zone to possible development. The forests form a 16-km-wide strip reaching 65 km from the Caribbean Sea to the Pacific Ocean and function as the water supply for the canal and as home to one of the world's richest terrestrial biotas. We present an overview of the distribution of bird diversity in the forests of the canal area based on 10 years of inventories. A total of 498 terrestrial species has been recorded, of which 177 occur only in lowland forests. More species reside in Caribbean-than in Pacific-slope forests and in the largest forest tracts. The Panamanian government, recognizing the importance of the forests for protection of biodiversity and for proper functioning of the canal, has created two national parks and a national monument in the canal area. One large park, Soberania National Park, currently contains 92% of the region's forest-dwelling species. Two large tracts on the Caribbean coast, the Achiote Road forest and the Fort Sherman forest, are not designated as national parks but are recognized as important forest areas. Those two forests harbor species found nowhere else in the canal corridor. Extensive fragmentation, disconnection of forested corridors between foothills and lowlands, and anthropogenic degradation of forests near towns have altered regional bird-community dynamics. Some dynamics occur on large spatial scales, such as the poorly understood movements of elevational and transisthmian migrants. Long-term maintenance of bird species diversity in the canal area will require preservation of the large forest tracts and reestablishment of a forested connection from the canal corridor lowlands to the Chagres lowlands and foothills in the east. Such conservation activities will be challenging to execute given the region's growing human population and desires for a stronger national economy. We recommend protection of remaining forests and active enforcement of protection laws to reduce hunting and further intrusions. Distribución de la Diversidad de Aves en un Paisaje Neotropical Vulnerable Resumen: El reciente retiro de militares de E.U.A. de la República de Panamá ha expuesto 64,000 ha de bosque bajo en la antigua Zona del Canal a la posibilidad del desarrollo. Los bosques forman una franja de 16 km de ancho que se extiende desde 65 km del Mar Caribe hasta el Océano Pacífico y funciona como fuente de agua para el canal y como hábitat para una de las biotas más ricas del mundo. Presentamos una visión general de la distribución de la diversidad de aves en los bosques delárea del canal basada en 10 años de inventarios. Se han registrado 498 especies terrestres, de las cuales 177 solo ocurren en bosques bajos. Más especies residen en los bosques del lado de Caribe que del Pacífico y en las mayores extensiones de bosques.El gobierno panameño, reconociendo la importancia de los bosques para la protección de la biodiversidad y para el adecuado funcionamiento del canal, ...

Environmental correlates of avian diversity in lowland Panama rain forests

“…Condit (1998), Pyke et al (2001) and Schnitzer (2005) showed how plant species richness varies from the drier Pacific coast to the wetter, evergreen forests on the Caribbean coast. Condit et al (2001) and Robinson et al (2004) documented broadscale distribution patterns of forest bird richness, revealing the lowest species richness (12 species) near the Pacific coast and more than 170 species in Caribbean coastal forests. In the latter studies, only forest area and rainfall were evaluated as possible drivers of bird species richness patterns, although other factors could also be involved.…”

Causes of habitat loss in a Neotropical landscape: The Panama Canal corridor

“…Biodiversity increases from the Pacific to the Caribbean along a steep rainfall gradient (Condit, 1998;Condit et al, 2001;Pyke et al, 2001). For example, forest bird species richness increases from 4 dry-forest specialists to more than 170 wet-forest specialists along this gradient (Ridgely and Gwynne, 1989;Angehr, 2006;Robinson et al, 2004;Rompre et al, 2007). The same pattern occurs in tree species richness (Condit, 1998;Pyke et al, 2001).…”

“…This part of Central America harbours forests rich in biodiversity neighbouring two growing cities (including the country's capital) within a relatively small area . After nearly a century of U.S. military presence, which limited economic and development opportunities in the canal region, departure of the U.S. in December 1999 released lands for possible conversion by Panamanians (Cho, 2001;Condit et al, 2001;Dale et al, 2003;Robinson et al, 2004). New roads, railroads, and bridges quickly followed as urban sprawl around Panama City increased (Cho, 2001).…”

“…Historically, biophysical factors such as mountains with steep slopes, dense vegetation, and high annual rainfall influenced which habitats were occupied by humans (Suarez, 1981). Yet, today, despite a human population of more than 1.3 million and intense economic pressures, 50% of the region still has forest (HeckadonMoreno et al, 1999;Condit et al, 2001;Ibanez et al, 2002;Robinson et al, 2004). These forests are still considered vital to protect the Canal watershed and to preserve the regional hydrologic system for Canal operations (Heckadon-Moreno et al, 1999).…”

“…Studies of birds, for example, show that both fragmentation and habitat loss reduce diversity (Robinson et al, 2000(Robinson et al, , 2004Laurance et al, 2002b;Gaston et al, 2003;Waltert et al, 2005;Rompre et al, 2007). Major factors associated with fragmentation and habitat loss, and therefore loss of biodiversity, are high levels of human population density (Cincotta et al, 2000;McKee et al, 2003;Scharlemann et al, 2004), density of roads (Maki et al, 2001;Laurance et al, 2002aLaurance et al, , 2006Gutzwiller and Barrow, 2003;Glennon and Porter, 2005), changes in agricultural practices (Meyer and Turner, 1992;Huston, 1993), logging (Kohleretal., 2002;Rudel, 2005), and hunting (Brashares et al, 2001;Laurance et al, 2006).…”