Climate change will reduce suitable Caatinga dry forest habitat for endemic plants with disproportionate impacts on specialized reproductive strategies

Abstract

Global climate change alters the dynamic of natural ecosystems and directly affects species distributions, persistence and diversity. The impacts of climate change may lead to dramatic changes in biotic interactions, such as pollination and seed dispersal. Life history traits are extremely important to consider the vulnerability of a species to climate change, producing more robust models than those based primarily on species distributions. Here, we hypothesized that rising temperatures and aridity will reduce suitable habitats for the endemic flora of the Caatinga, the most diverse dry tropical forest on Earth. Specifically, species with specialized reproductive traits (e.g. vertebrate pollination, biotic dispersal, obligatory cross-pollination) should be more affected by climate change than those with generalist traits. We performed two ecological niche models (current and future) to simulate the effects of climate change on the distribution area of endemic species in relation to life-history traits. We used the MIROC-ESM and CCSM4 models for both intermediate (RCP4.5) and highest predicted (RCP8.5) GHG emission scenarios, with a resolution of 30' (~1 km2). Habitat with high occurrence probability (>80%) of endemic species will be reduced (up to ~10% for trees, ~13% for non-arboreous, 10-28% for species with any pollination/reproductive system), with the greatest reductions for species with specialized reproductive traits. In addition, the likely concentration of endemic plants in the extreme northeastern portion of the Caatinga, in more mesic areas, coincides with the currently most human-modified areas of the ecosystem, which combined with climate change will further contract suitable habitats of endemic species. In conclusion, plant species endemic to the Caatinga are highly vulnerable to even conservative scenarios of future climate change and may lose much of their climatic envelopes. New protected areas should be located in the northeastern portion of the Caatinga, which hosts a more favorable climate, but is currently exposed to escalating agricultural intensification.

Fig 1. Location and geographic limits of the Caatinga.

(A) Geographical location of the Caatinga in South America and (B) Phytogeographic domains in northeastern Brazil. Source of the shapes of the Brazilian phytogeographic domains: MMA-Ministério do Meio Ambiente, Brazil (public domain) (available for download at http://mapas.mma.gov.br/i3geo/datadownload.htm and http://mapas.mma.gov.br/mapas/aplic/probio/datadownload.htm?/caatinga/dados/shape_file/).

Fig 2. Distribution of suitable habitats of plant species endemic to the Caatinga.

(A) During both the current period and two future scenarios, between 2070 and 2099, including a more optimistic (RCP4.5) (B) and a more pessimistic (RCP8.5) (C) projection. Solid dots in A indicate locations of the sampled species. Source of the shapes of the Brazilian and Caatinga boundaries, and protected areas: MMA-Ministério do Meio Ambiente, Brazil (public domain) (available for download, respectively, at http://mapas.mma.gov.br/i3geo/datadownload.htm; http://mapas.mma.gov.br/mapas/aplic/probio/datadownload.htm?/caatinga/dados/shape_file/); http://www.mma.gov.br/areas-protegidas/cadastro-nacional-de-ucs/dados-georreferenciados.html.

Fig 3. Reduction of suitable Caatinga habitat (probability of occurrence > 80%) for endemic flowering plant species in the current period and in two future scenarios, an optimistic (RCP4.5) and a pessimistic (RCP8.5).

(A) Habit (N = 76). (B) Pollination systems (N = 64). (C) Reproductive systems (N = 25). (D) Dispersal modes (N = 62). Different letters below the boxplots indicate statistical significance of post-hoc comparisons at P < 0.05.

Fig 4

Distribution of suitable habitat for arboreous species (A, B and C) and non-arboreous species (D, E and F) endemic to the Caatinga during both the present and two future scenarios, between 2070 and 2099, including an optimistic (RCP4.5) and a pessimistic (RCP8.5) scenario. Solid dots in A and D indicate locations of the sampled species. Source of the shapes of the Brazilian and Caatinga boundaries: MMA-Ministério do Meio Ambiente, Brazil (public domain) (available for download at http://mapas.mma.gov.br/i3geo/datadownload.htm and http://mapas.mma.gov.br/mapas/aplic/probio/datadownload.htm?/caatinga/dados/shape_file/).

Fig 5

Distribution of suitable habitat for plant species endemic to the Caatinga with either generalist (A, B and C) or specialized (D, E and F) pollination systems in both the present and two futures scenarios, between 2070 and 2099, including an optimistic (RCP4.5) and a pessimistic (RCP8.5) scenario. Solid dots in A and D indicate locations of the sampled species. Source of the shapes of the Brazilian and Caatinga boundaries: MMA-Ministério do Meio Ambiente, Brazil (public domain) (available for download at http://mapas.mma.gov.br/i3geo/datadownload.htm and http://mapas.mma.gov.br/mapas/aplic/probio/datadownload.htm?/caatinga/dados/shape_file/).

Fig 6

Distribution of suitable habitat for plants species endemic to the Caatinga with either self-compatible (A, B and C) or self-incompatible/dioecious (i.e. obligatory cross-pollination) (D, E and F) reproductive systems in the present and two future scenarios, between 2070 and 2099, including an optimistic (RCP4.5) and a pessimistic (RCP8.5). Solid dots in A and D indicate locations of the sampled species. Source of the shapes of the Brazilian and Caatinga boundaries: MMA-Ministério do Meio Ambiente, Brazil (public domain) (available for download at http://mapas.mma.gov.br/i3geo/datadownload.htm and http://mapas.mma.gov.br/mapas/aplic/probio/datadownload.htm?/caatinga/dados/shape_file/).

Fig 7

Distribution of suitable habitat for plant species endemic to the Caatinga with either abiotic (A, B and C) or biotic (D, E and F) seed dispersal modes in both the present and two futures scenarios between 2070 and 2099, including an optimistic (RCP4.5) and a pessimistic (RCP8.5). Solid dots in A and D indicate locations of the sampled species. Source of the shapes of the Brazilian and Caatinga boundaries: MMA-Ministério do Meio Ambiente, Brazil (public domain) (available for download at http://mapas.mma.gov.br/i3geo/datadownload.htm and http://mapas.mma.gov.br/mapas/aplic/probio/datadownload.htm?/caatinga/dados/shape_file/).