perspective: The responses of tropical forest species to global climate change: acclimate, adapt, migrate, or go extinct?

Abstract

Understanding the effects of climate change on natural systems has been referred to as "a grand challenge in ecology" (Thuiller 2007). Nowhere is this challenge more poignant, and perhaps more daunting, than in tropical forests. Despite covering a tiny fraction of the Earth's surface, tropical forests harbor the majority of known and unknown species (Raven 1988, Dirzo and Raven 2003, Joppa et al. 2011a), sequester vast amounts of carbon (Saatchi et al. 2011, Baccini et al. 2012), and support many millions of humans directly through the production of food and other resources (Fa et al. 2002, Milner-Gulland and Bennett 2003), or indirectly through a diverse range of ecosystem services (Costanza et al. 1997, Cincotta et al. 2000, Naidoo et al. 2008). In this review, we discuss the potential effects of ongoing and future climate change on tropical forests and specifically tropical forest tree species, with an acknowledged bias towards Amazonian and Andean species. There are only four possible responses of any species, including tropical trees, to global climate change: (1) individuals can acclimate to changes in climate through phenotypic plasticity Abstract. In the face of ongoing and future climate change, species must acclimate, adapt or shift their geographic distributions (i.e., "migrate") in order to avoid habitat loss and eventual extinction. Perhaps nowhere are the challenges posed by climate change more poignant and daunting than in tropical forests, which harbor the majority of Earth's species and are facing especially rapid rates of climate change relative to current spatial or temporal variability. Considering the rapid changes in climate predicted for the tropics, coupled with the apparently low capacities of tropical tree species to either acclimate or adapt to sustained changes in environmental conditions, it is believed that the greatest hope for avoiding the loss of biodiversity in tropical forest is species migrations. This is supported by the fact that topical forests responded to historic changes in climate (e.g., post glacial warming) through distributional shifts. However, a great deal of uncertainty remains about whether tropical forest plant species can migrate, and if so, whether they can migrate at the rates required to keep pace with accelerating changes in multiple climatic factors in conjunction with ongoing deforestation and other anthropogenic disturbances. In order to resolve this uncertainty, as will be required to predict, and eventually mitigate, the impacts of global climate change on tropical and global biodiversity, more basic data are required on the distributions and ecologies of tens of thousands of plant species, in combination with more directed studies and large-scale experimental manipulations.

The inability of tropical cloud forest species to invade grasslands above treeline during climate change: potential explanations and consequences

“…Areas where cloud forests are currently distributed have served in the past, and could potentially serve in the future, as climate refugia for tropical lowland species requiring cooler climates in the face of increasing global temperatures (Bush et al , Feeley et al ). Evidence of distributional shifts of cloud forest plant species is currenty limited to two studies – one from Costa Rica and one from the Peruvian Andes (Feeley et al , ).…”

“…Stationary tropical treeline forests will result in one of two scenarios for cloud forest species’ ranges; 1) ranges can stay relatively stable and individuals can acclimate or adapt to the changing environmental conditions in situ, or 2) species can lose range area at their lower elevational limit while failing to gain area at their high elevational limit, resulting in decreasing range area and population sizes (Feeley et al ). Current evidence suggests that acclimation or adaptation of tropical cloud forest trees is unlikely, especially considering the rate of current climate change and the long life span and generation times of most tree species (Clark et al , Feeley et al ). In addition, many tropical cloud forest species are already exhibiting range shifts or contractions, especially at their low elevation limits, in response to rising temperature (Feeley et al , ).…”

Compositional shifts in Costa Rican forests due to climate‐driven species migrations

“…In contrast to the temperate zones, examples of range shifts from the tropics remain extremely sparse (reviewed in Feeley et al ., ). Indeed, in the meta‐analysis described above only 2 studies from the tropics were included, representing a combined total of just 160 species [130 species of moths on Mt.…”

“…This despite the fact that the tropics house the majority of Earth's species (Dirzo & Raven, ; Joppa et al ., ; Raven, ), many of which are expected to be especially sensitive to climate change due to their narrow climatic tolerances (Huey et al ., ; Janzen, ; McCain, ; Sunday et al ., ). This paucity of studies and data is especially prevalent for tropical plants (Feeley et al ., ), highlighted by the complete absence of studies of tropical plants from the meta‐analysis mentioned above (Chen et al ., ). In fact, we know of only two studies documenting range shifts in tropical plant species.…”

Multilocus Analyses Reveal Postglacial Demographic Shrinkage of Juniperus morrisonicola (Cupressaceae), a Dominant Alpine Species in Taiwan

“…morrisonicola might be threatened by the historical alpine glaciers. The surviving populations might have been shaped by local adaptation, range shifts, and other stochastic factors [67–69]. Of these, range reduction is likely to cause the loss of genetic diversity [70], which in turn may severely limit the species’ responses to environmental change.…”