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Combined impacts of global changes on biodiversity across the USA.

Bellard C, Leclerc C, Courchamp F - Sci Rep (2015)

Bottom Line: Most studies of the effects of global changes on biodiversity focus on a single threat, but multiple threats lead to species extinction.These high cumulative impact values are due mainly to the presence of invasive species, climate change, cropland and pasture areas; additionally, a significant proportion of endemic species are vulnerable to some of these threats where they occur.This analysis provides a useful means of identifying where conservation measures and monitoring programs that should consider multiple threats should be implemented in the future.

View Article: PubMed Central - PubMed

Affiliation: 1] Genetics, Evolution &Environment, Div Biosciences, Center for Biodiversity, Environment &Research, University College of London [2] Ecologie, Systématique &Evolution, UMR CNRS 8079, Univ. Paris-Sud, F-91405 Orsay Cedex, France.

ABSTRACT
Most studies of the effects of global changes on biodiversity focus on a single threat, but multiple threats lead to species extinction. We lack spatially explicit assessments of the intensity of multiple threats and their impacts on biodiversity. Here, we used a novel metric of cumulative threats and impacts to assess the consequences of multiple threats on 196 endemic species across the USA. We predict that large areas with high cumulative impact scores for amphibians, birds, mammals, and reptiles will be concentrated in the eastern part of the USA by the 2050 s and 2080  . These high cumulative impact values are due mainly to the presence of invasive species, climate change, cropland and pasture areas; additionally, a significant proportion of endemic species are vulnerable to some of these threats where they occur. This analysis provides a useful means of identifying where conservation measures and monitoring programs that should consider multiple threats should be implemented in the future.

No MeSH data available.


Cumulative threats in the 2080 s under the A1B emission scenario:(A) Boxplot of the ten most affected states in the USA under the A1B emission scenario. The horizontal grey line represents the median value of cumulative threats across the USA. (B) Spatial distribution figure created in R 3.1.1.
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f2: Cumulative threats in the 2080 s under the A1B emission scenario:(A) Boxplot of the ten most affected states in the USA under the A1B emission scenario. The horizontal grey line represents the median value of cumulative threats across the USA. (B) Spatial distribution figure created in R 3.1.1.

Mentions: We also investigated the cumulative threats (that is, the total threat intensity values) occurring across the USA. On average, a minimum of 1.5 cumulative threat values per pixel occurred for the whole country. We observed substantial heterogeneity throughout the country, with a clear pattern of high cumulative threat values in the eastern part; low cumulative threat values are prevalent across most of the western part of the country under the two emission scenarios. Areas in the eastern half of the USA will be exposed to a minimum of two different threats simultaneously; the central part of the USA was predicted to be exposed to moderate cumulative threat values <2). In addition, the western part was predicted to be relatively less threatened except for the western coastline, which was exposed to high cumulative threat values (<4) (Fig. 2A; Figure S2). This trend becomes evident when summarizing the cumulative threat by state (Fig. 2Table S3). The District of Columbia and Delaware were the areas most exposed to cumulative threat values under the A1B and B2A emission scenarios (median ≈3, Table S3). Maryland and New Jersey were also predicted to be affected by high cumulative threat values under the A1B emission scenarios but by lower values under the B2A emission scenarios. We also investigated exposure of species to cumulative threat values. Species at higher risk of extinction (and likely to have a smaller range size according to our data) were exposed to lower values of cumulative threats compared to species at low risk of extinction (with larger range size, except for “critically endangered” classified species, Figure S3). One of the explanation of this result might be due to the lower probability to be exposed to a high number of threat when the species range size is small. Moreover, the species that are at high risk of extinction were mainly located in the western part of U.S., where we found lower values of cumulative threats. In addition, related species of amphibians and mammals were generally exposed to similar cumulative threat values, because the phylogenetic signal was strong for these two groups (Supplementary Material 1).


Combined impacts of global changes on biodiversity across the USA.

Bellard C, Leclerc C, Courchamp F - Sci Rep (2015)

Cumulative threats in the 2080 s under the A1B emission scenario:(A) Boxplot of the ten most affected states in the USA under the A1B emission scenario. The horizontal grey line represents the median value of cumulative threats across the USA. (B) Spatial distribution figure created in R 3.1.1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493580&req=5

f2: Cumulative threats in the 2080 s under the A1B emission scenario:(A) Boxplot of the ten most affected states in the USA under the A1B emission scenario. The horizontal grey line represents the median value of cumulative threats across the USA. (B) Spatial distribution figure created in R 3.1.1.
Mentions: We also investigated the cumulative threats (that is, the total threat intensity values) occurring across the USA. On average, a minimum of 1.5 cumulative threat values per pixel occurred for the whole country. We observed substantial heterogeneity throughout the country, with a clear pattern of high cumulative threat values in the eastern part; low cumulative threat values are prevalent across most of the western part of the country under the two emission scenarios. Areas in the eastern half of the USA will be exposed to a minimum of two different threats simultaneously; the central part of the USA was predicted to be exposed to moderate cumulative threat values <2). In addition, the western part was predicted to be relatively less threatened except for the western coastline, which was exposed to high cumulative threat values (<4) (Fig. 2A; Figure S2). This trend becomes evident when summarizing the cumulative threat by state (Fig. 2Table S3). The District of Columbia and Delaware were the areas most exposed to cumulative threat values under the A1B and B2A emission scenarios (median ≈3, Table S3). Maryland and New Jersey were also predicted to be affected by high cumulative threat values under the A1B emission scenarios but by lower values under the B2A emission scenarios. We also investigated exposure of species to cumulative threat values. Species at higher risk of extinction (and likely to have a smaller range size according to our data) were exposed to lower values of cumulative threats compared to species at low risk of extinction (with larger range size, except for “critically endangered” classified species, Figure S3). One of the explanation of this result might be due to the lower probability to be exposed to a high number of threat when the species range size is small. Moreover, the species that are at high risk of extinction were mainly located in the western part of U.S., where we found lower values of cumulative threats. In addition, related species of amphibians and mammals were generally exposed to similar cumulative threat values, because the phylogenetic signal was strong for these two groups (Supplementary Material 1).

Bottom Line: Most studies of the effects of global changes on biodiversity focus on a single threat, but multiple threats lead to species extinction.These high cumulative impact values are due mainly to the presence of invasive species, climate change, cropland and pasture areas; additionally, a significant proportion of endemic species are vulnerable to some of these threats where they occur.This analysis provides a useful means of identifying where conservation measures and monitoring programs that should consider multiple threats should be implemented in the future.

View Article: PubMed Central - PubMed

Affiliation: 1] Genetics, Evolution &Environment, Div Biosciences, Center for Biodiversity, Environment &Research, University College of London [2] Ecologie, Systématique &Evolution, UMR CNRS 8079, Univ. Paris-Sud, F-91405 Orsay Cedex, France.

ABSTRACT
Most studies of the effects of global changes on biodiversity focus on a single threat, but multiple threats lead to species extinction. We lack spatially explicit assessments of the intensity of multiple threats and their impacts on biodiversity. Here, we used a novel metric of cumulative threats and impacts to assess the consequences of multiple threats on 196 endemic species across the USA. We predict that large areas with high cumulative impact scores for amphibians, birds, mammals, and reptiles will be concentrated in the eastern part of the USA by the 2050 s and 2080  . These high cumulative impact values are due mainly to the presence of invasive species, climate change, cropland and pasture areas; additionally, a significant proportion of endemic species are vulnerable to some of these threats where they occur. This analysis provides a useful means of identifying where conservation measures and monitoring programs that should consider multiple threats should be implemented in the future.

No MeSH data available.