Effectiveness of Panama as an intercontinental land bridge for large mammals, Meyer et al. 2019

One of the world’s largest corridor projects is the Mesoamerican Biological Corridor (MBC). Initiated in the 1990s, the MBC aims to connect protected areas between southeastern Mexico and Panama [Meyer 2019: 2].

The ecological functionality of the MBC has not been much assessed, in part because direct approaches to measuring connectivity are costly and challenging. In this study, researchers used a simpler, indirect approach to measure forest connectivity through Panama for nine mammals. Using camera traps (cameras that are automatically triggered by a change in some activity in the vicinity, like the presence of an animal), they documented the presence (or absence) of these mammals in 28 forest sites along the Atlantic coast. The corridor was presumed to be functioning for animals whose presence was established across the entire length of the monitored range.

The species monitored in this study are forest specialists, including ungulates, carnivores and an insectivore, all of which are threatened by habitat loss and hunting, some more than others. Of the 43% of land in Panama that is forested, 44% is protected, mostly along the Atlantic coast. Steady economic development threatens remaining ecosystems with investments in large infrastructure projects, real estate, mining, tourism, and energy.

Large mammals are an indicator species for the success of conservation efforts. This is because:

Large mammals are generally at a higher risk of extinction in disturbed landscapes than other taxa because their large home ranges and low population densities at broad spatial scales mean their populations are more likely to be fragmented and because they are heavily hunted [Meyer 2019: 3].

The researchers found that even the four most prevalent species in the study are susceptible to population fragmentation by any further habitat loss.

We found that there was little connectivity for white-lipped peccary [a pig-like animal] and white-tailed deer and that, although 4 of the species (collared peccary, red brocket deer, puma, and ocelot [a wild cat]) occurred in most of the sites, a small decrease in connectivity of 20% would disrupt their continuous distributions across Panama. White-lipped peccary, giant anteater, white-tailed deer, jaguar, and tapir [a pig-like animal with a short trunk] had lower probability of occurring in all the sites and were therefore even more at risk of connectivity loss, as evidenced by >1 connectivity gap. This indicates the MBC may not function for the majority of species, especially considering we did not account for potential effects of hunting, which would make connectivity even more challenging [Meyer 2019: 8].

Citing imminent development projects, such as a new road that will pass through the forested northern coast and associated large hotel projects, the authors predict that ongoing loss of connectivity is likely. Moreover, the deteriorating condition of the corridor in Panama bodes poorly for the MBC overall.

The disruption of connectivity between tropical forests in Central America, and hence the possible separation of mammal populations, is an indicator of the overall functioning of the MBC for wildlife [Meyer 2019: 11].