The Americas contain highly biodiverse yet vulnerable ecosystems, with many threatened species inadequately protected. Finer-scale, localized habitat assessments are crucial for effective conservation planning, but continental-scale high-resolution vegetation maps remain limited. This study addresses this gap by identifying critical vegetation types across the Americas using the standardized framework of the International Vegetation Classification (IVC) system at the macrogroup level, representing the finest vegetation classification available across the region, as well as the highest-resolution Area of Habitat (AOH) maps currently available for birds and mammals. By combining these high-resolution IVC macrogroup maps with detailed AOH maps, we highlight at-risk vegetation types based on 1) threatened and macrogroup-associated species (species that have at least 50% of their AOH in one macrogroup), 2) current protection levels, and 3) projected threats from land use changes, and 4) develop a conservation value index (CVI) that accounts for all these factors. The results highlighted the remarkable diversity of high conservation value macrogroups across the Americas, emphasizing their significance in regions such as the Andes, montane Mesoamerica, the Caribbean, Brazil's Cerrado, and the Atlantic Forest. Among the highest-scoring macrogroups, the Northern Andean Montane & Upper Montane Humid Forest emerged as critically important, harboring a high number of threatened and macrogroup-associated species. Other macrogroups of immediate conservation concern include the Brazilian Atlantic Montane Humid Forest, Pacific Mesoamerican Seasonal Dry Forest, Caribbean Lowland Humid Forest, and Central Midwest Oak Forest, Woodland and Savanna. However, the study revealed that nearly three-quarters of the over 300 macrogroups in the Americas fall below the global target of 30% protection. Notably, a fifth of all species were macrogroup-associated species, including over 40% of threatened species. Our findings emphasize the need for targeted conservation strategies that consider finer-scale habitat classifications and paired with high-quality species distribution data to guide conservation strategies for biodiversity across the Americas.

Data Collection

Vegetation Types

The study utilized the International Vegetation Classification (IVC) system, focusing on the macrogroup level consisting of 321 natural vegetation types. This systematic approach enables a detailed vegetation analysis based on ecological criteria. The size of these macrogroups ranged significantly, with the vegetation map having a spatial resolution of 90 x 90 meters, reflecting vegetation as of 2010. All maps were resampled for consistent resolution.

Species Distribution

Area of Habitat (AOH) maps from Lumbierres et al. (2022) were used to assess terrestrial birds and mammals' habitat patterns in the Americas. The dataset included 6,204 species, with 1,868 mammals and 4,336 birds, offering a detailed 100 x 100-meter resolution. Migratory birds had separate AOH maps for different life stages, which were combined for analysis.

Protected Areas

Polygon data from the World Database of Protected Areas (WDPA) was employed to evaluate the protection status of IVC macrogroups. The database includes 273,263 polygons across six protection classes, and all terrestrial areas and OECMs were considered.

Projected Land-use

Future anthropogenic land-use was projected using high-resolution models from Chen et al. (2020), covering various SSP and RCP scenarios. The SSP3-RCP4.5 scenario was specifically chosen for its moderate outlook. Land types were grouped, and the projected percentage of anthropogenic land use by 2030 was calculated to align with the Aichi Biodiversity Targets.

Data Processing

An overlay analysis of IVC macrogroup and AOH data determined species composition within each macrogroup. Migratory birds were handled separately, combining three AOH maps. Species were then filtered by threatened status using IUCN Red List categories. Macrogroup-associated species were defined as having at least half of their AOH within one macrogroup. Protected area coverage was assessed by overlaying macrogroup and protected area data. Future land use data was integrated to estimate land conversion probabilities by 2030. These steps were used to develop a Conservation Value Index (CVI).

Conservation Value Index

The CVI was calculated using a formula that equally weighs the number of threatened species, macrogroup-associated species, the percentage of macrogroup protection, and average land use within the macrogroup. The index offers a composite metric for assessing vegetation types for conservation, with adaptable parameters suitable for various contexts.