Introduction
Understanding
species distributions is fundamental for conservation and management.
Accurate maps of species distributions enables assessment of
conservation priorities worldwide, based on diversity, threat or
endemism, facilitating the development of targeted conservation
strategies. Thus, to perform such prioritizations or gap analyses, the
spatial accuracy of species ranges is crucial. In the last two decades,
IUCN and similar species range maps have become a global currency for
the assessment of species distributions across scales and subsequent
conservation funding (Jetz et al. 2012, Jenkins et al. 2013, Brooks et
al. 2019). Though these maps have been created for varying purposes by
different groups, they are now used for global biodiversity analyses,
and little has been done to test whether they are truly fit for this
purpose.
Species
range modeling is highly-sensitive to the data and methods employed. For
instance, even basic means of trimming species IUCN ranges using habitat
or elevation changes the RedList status of many species via
corresponding distributional changes (Ocampo-Peñuela et al. 2016, Li et
al. 2017). The reliability of such analyses is crucial not only to
apportion adequate and appropriate conservation efforts, but to
understand even basic biodiversity patterns, as errors could highlight
the wrong areas and species, and with limited resources available this
translates to failures to conserve areas and ecosystems critically
needing protection.
Unfortunately,
accurate and reliable data are rare for most taxonomic groups due to
intense sampling biases (Hughes et al. in review ). As a
consequence,
IUCN and similar data
underlie
countless studies, including those on distribution (Buckley & Jetz
2008, Holt et al. 2013, Rissler & Smith 2010), climate change (Akcakaya
et al. 2006, Sandel et al. 2011, Sekerciuglu et al. 2012), and
especially conservation (Jenkins et al. 2013, La Saout et al. 2013, Jetz
et al. 2014, Pouzols et al. 2014, Jenkins et al. 2015, Meyer et al.
2015, Runge et al. 2015, Ocampo-Peñuela et al. 2016, Betts et al. 2017,
Li et al. 2017, Moran & Kanemoto 2017, Brooks et al. 2019, Mason et al.
2020). These include analyses at varying resolutions, though
10km2 is a common resolution since these data are made
available for download and analysis (https://biodiversitymapping.org),
yet many of these use the maps at a higher resolution than has been
shown appropriate Guidance
(https://www.conservationtraining.org/enrol/index.php?id=156)
states that distribution data should be utilized in developing species
range polygons, yet the adherence to these guidelines is not apparent.
It is dangerous to use questionable data for real-world conservation,
and researchers should carefully assess the limits of the data before
applying them to real-world issues.
Here, we test the widespread assumption that the most up-to-date expert
range maps (ERMs) (for mammals, odonata, amphibians, birds, and
reptiles) provide consistent and standardized species range estimates,
exploring whether these range boundaries are associated with
administrative divisions. We also assess the proportion of species
distribution points for each species falling within their designated
IUCN ranges. We discuss and showcase alternative means of mapping
diversity patterns, and demonstrate the tradeoff between different
approaches, and the limits of applications for each. Understanding
biases and inconsistencies helps inform appropriate use and ensures data
are fit for purpose, and to make better use of available data to
effectively inform research and management decisions based on a clearer
understanding of species and richness patterns.