Effectiveness of protected areas in conserving tropical forest birds

Abstract

Protected areas (PAs) are the cornerstones of global biodiversity conservation efforts, but to fulfil this role they must be effective at conserving the ecosystems and species that occur within their boundaries. Adequate monitoring datasets that allow comparing biodiversity between protected and unprotected sites are lacking in tropical regions. Here we use the largest citizen science biodiversity dataset - eBird - to quantify the extent to which protected areas in eight tropical forest biodiversity hotspots are effective at retaining bird diversity. We find generally positive effects of protection on the diversity of bird species that are forest-dependent, endemic to the hotspots, or threatened or Near Threatened, but not on overall bird species richness. Furthermore, we show that in most of the hotspots examined this benefit is driven by protected areas preventing both forest loss and degradation. Our results provide evidence that, on average, protected areas contribute measurably to conserving bird species in some of the world's most diverse and threatened terrestrial ecosystems.

Fig. 1. Regions covered by the present study (i.e. intersection between eight biodiversity hotspots and the “tropical and subtropical moist broadleaf forests” biome).

Acronyms as in Figs. 3 and 4: ATL (Atlantic Forest, N = 6760 checklists), AND (Tropical Andes, N = 17,758), TUM (Tumbes-Chocó-Magdalena, N = 1188), MES (Mesoamerica, N = 32,784), EAS (Eastern Afromontane, N = 1097), GHA (Western Ghats and Sri Lanka, N = 2646), IND (Indo-Burma, N = 2996), and SUN (Sundaland, N = 1548). More details in Supplementary Fig. 1.

Fig. 2. Framework of the analyses performed to investigate the effectiveness of protected areas at retaining bird diversity.

Analysis I: effect of protected areas on bird diversity measured through four indices of bird species richness (all species, forest-dependent species, endemic species, threatened, and near threatened species). The asterisk indicates species of conservation concern. Analysis II: effects of protected areas on forest presence (IIa), local deforestation rates (IIa′), and on three measures of forest quality (canopy height, forest contiguity, and wilderness; IIb). Analysis III: effects of forest presence (IIIa), and of each of the three measures of forest quality and of the residual effect of protected areas (IIIb) on bird diversity.

Fig. 3. Effect of protected areas on bird diversity per hotspot, for four bird diversity indices (analysis I).

a Overall species richness. b Forest-dependent species richness. c Endemic species richness. d Richness in threatened and Near Tthreatened species. Coefficients correspond to the estimates of GAM models; significance is given by the P value (***<0.001 < **<0.01 < *<0.05, see details in Supplementary Table 3) and the 95% confidence interval around GAM coefficients (vertical error bars). Hotspots: ATL (Atlantic Forest), AND (Tropical Andes), TUM (Tumbes-Chocó-Magdalena), MES (Mesoamerica), EAS (Eastern Afromontane), GHA (Western Ghats and Sri Lanka), IND (Indo-Burma), and SUN (Sundaland). Number of checklists per hotspot is specified below hotspots names; more detailed results in Supplementary Table 1.

Fig. 4. Effects of protected areas on forest cover, and effects of forest cover on bird diversity, per hotspot.

Bars: effects of protected areas on forest presence (a analysis IIa) or on deforestation rates between 2000 and 2019 (b analysis IIa′); coefficients correspond to the estimates of GAM models; significance given by P value (***<0.001 < **<0.01 < *<0.05), and 95% confidence interval around GAM coefficients (vertical error bars). Feathers: colour represents the effect sign (blue: positive; red: negative; white: non-significant [P value > 0.05]) of forest presence on each of the bird diversity variables (All spp., overall species richness; For. Dep., richness in forest-dependent species; Endemic, richness in endemic species; Thr + NT, richness in threatened and Near Threatened species). Hotspots: ATL (Atlantic Forest), AND (Tropical Andes), TUM (Tumbes-Chocó-Magdalena), MES (Mesoamerica), EAS (Eastern Afromontane), GHA (Western Ghats and Sri Lanka), IND (Indo-Burma), and SUN (Sundaland). Number of checklists per hotspot is specified below hotspots names; more detailed results in Supplementary Table 1 and Supplementary Fig. 3.

Fig. 5. Effects of protected areas on forest quality, and effects of forest quality on bird diversity, per hotspot.

Bars: effects of protected areas on forest quality (a canopy height; b forest contiguity; c wilderness; d protected area residuals; analysis IIb); coefficients correspond to the estimates of GAM models; significance given by P value (***<0.001 < **<0.01 < *<0.05), and 95% confidence interval around GAM coefficients (vertical error bars). Feathers: colour represents the effect sign (blue: positive; red: negative; white: non-significant [P value > 0.05]) of each habitat quality variable on each of the bird diversity variables (All spp., overall species richness; For. Dep., richness in forest-dependent species; Endemic, richness in endemic species; Thr + NT, richness in threatened and Near Threatened species). Hotspots: ATL (Atlantic Forest), AND (Tropical Andes), TUM (Tumbes-Chocó-Magdalena), MES (Mesoamerica), EAS (Eastern Afromontane), GHA (Western Ghats and Sri Lanka), and IND (Indo-Burma), SUN (Sundaland). Number of checklists per hotspot is specified below hotspots names (only forest checklists in this analysis); more detailed results in Supplementary Table 1 and Supplementary Fig. 3.