We are starting to explore the use of 360degree spherical images for showing off the cool places around the world where we work. This is just a test to see if we can successfully embed one of these images in the blog. This image is of the walkway on University of Miami’s Coral Gables campus…
Next month, experts in climate reconstruction will meet to create a consensus record of atmospheric CO2 over the past 66 million years. Stomata will play an important role in the coming meeting when paleoclimatologists reconcile their calculation using leaf gas exchange in fossil leaves with other sources1.
It was Woodward in 1987 who first observed that a significant inverse relationship existed between plant stomatal density (number of stomata per mm2) and atmospheric CO2 concentration. Using herbarium specimens, he demonstrated that the stomatal densities and ratio in 8 temperate woody specimens collected 200 years ago were significantly higher than those of the same plant species today2.
In 2014, Franks et al.3 applied the same idea of counting stomata to fossil leaves and integrated their counts with the available models for leaf gas exchange. Another important parameter used in common leaf gas exchange analysis is the internal CO2 content. In fossil leaves, this concentration can be obtained using the isotopic signal of δ13C to discriminate between leaf and atmospheric carbon. A worrisome finding from this method is that the Earth’s climate could be more sensitive to CO2 concentrations than previously thought.
Understanding the sensitivity of climate to carbon dioxide concentrations is a key point in the discussions of climate change. Scientists are trying to come up with better methods, with less uncertainty, which can help arrive at more accurate conclusions about our past climate. Hopefully, the stomata in fossil leaves can help in this effort. Another promised result from the meeting is an open source paleo-pCO2 database.
Thanks to the people in the plant bio journal club for pointing out this news.
- Hand, E. Fossil leaves bear witness to ancient carbon dioxide levels. Science 355, 14–15 (2017).
- Woodward, F. I. Stomatal numbers are sensitive to increases in CO2 from pre-industrial levels. Nature 327, 617–618 (1987).
- Franks, P. J. et al. New constraints on atmospheric CO2 concentration for the Phanerozoic. Geophys. Res. Lett. 41, 4685–4694 (2014).
A version of this post has also been published as an online comment in PLoS Biology
In his recent meta-analysis, “Climate-Related Local Extinctions Are Already Widespread among Plant and Animal Species“, Wiens looked at changes in species ranges and local extinctions driven by climate change.
Wiens claims to have broad taxonomic and geographic coverage of studies. Unfortunately, this is not the case. In fact, from the true tropics (i.e., excluding studies from the Santa Catalina Mountains of Arizona, USA, the Appalachian Mountains of north Georgia, USA, and the high eastern Himalayas that Wiens categorizes as “tropical” for the purposes of his analyses), only 5 studies representing a total of just 341 species (35% of species, 18% of studies) are included. All but one of these tropical studies (of 55 Andean bird species) are from oceanic islands (Borneo [insects], New Guinea [birds], Madagascar [amphibians], and Hawaii [plants]). All tropical plants are represented by just 4 grasses in Hawaii.
The lack of data from the tropics is not Wiens’ fault but rather reflects a true underlying disparity in the state of knowledge about different systems of the world. Simply put, we know much more about the effects of climate change in North America and Europe than we do the effects of climate change in the tropics. That said, Wiens needs to be more forthright in acknowledging this disparity. Furthermore, given this extreme lack of data, it is clearly premature to conclude that “there were significant effects of climatic region overall, with extinction more common in tropical regions” and that “this pattern of more frequent tropical extinction arose from a much lower frequency of extinctions for temperate plants”. Four grasses from Hawaii tell us next to nothing about how the thousands of tropical plants are responding to climate change. Or even if we lump the tropics and subtropics together as does Wiens, 4 grasses from Hawaii, 27 mountain desert plants from Arizona and 124 high-elevation Himalayan plant species (all with ranges restricted to elevations >3500 m asl) provide little information about how the thousands of other tropical and subtropical plants are responding to climate change. The tropical data void is real and it is troublesome (Feeley et al. 2016a,b). But before we can begin to address this lack of data it needs to be acknowledged and recognized for the problem that it is.
Wiens JJ. 2016. Climate-Related Local Extinctions Are Already Widespread among Plant and Animal Species. PLOS Biology 14(12): e2001104. doi: 10.1371/journal.pbio.2001104
Feeley KJ, Stroud JT, and Perez TM. 2016. Most “global” reviews of species’ responses to climate change aren’t truly global. Diversity and Distributions. In Press.
Feeley KJ, Silman M, and Duque A. 2016. Where are the tropical plants? A call for better inclusion of tropical plants in studies investigating and predicting the impacts of climate change. Frontiers of Biogeography. 7(4). fb_27602.
Ken Feeley and Miles Silman have published a new article in the journal Diversity and Distributions entitled “Disappearing climates will limit the efficacy of Amazonian protected areas“. This article discusses how protected areas, while a powerful tool against traditional threats such as hunting and deforestation, will fail to protect many parts of the Amazon against rising temperatures. In other words, “protected areas are not a panacea and the current reserve system alone may be insufficient to conserve biodiversity in the face of rapidly rising temperatures. Migration, whether through explicit corridors or through landscapes of working forests managed to facilitate species movement, will be paramount in determining the future of Amazonia”.
A discussion of this article is featured in Mongabay
ABSTRACT: Amazonian forests support high biodiversity and provide valuable ecosystem services. Unfortunately, these forests are under extreme pressure from land use change and other anthropogenic disturbances. A recent study combined data from an Amazon-wide network of forest inventory plots with spatially explicit deforestation models to predict that by 2050, 36% or 57% of species will be ‘globally threatened’, as defined by IUCN Red List criteria, due to deforestation under Increased-Governance or Business-As-Usual scenarios, respectively. It was also predicted that the number of threatened species will drop by 29–44% if no deforestation occurs within protected areas. However, even the best-protected areas of the Amazon may still be susceptible to the effects of climate change and rising temperatures. To illustrate the potential dangers of climate change for Amazonian parks, we calculated the percentage of land area within all officially designated protected areas of tropical South America that will or will not have future temperature analogs under various scenarios of temperature change and park connectivity. We show that depending on the rate of warming and degree of connectivity, about 19–67% of protected areas will not have any temperature analogs in the near future (2050s). These results help to emphasize that protected areas are not immune to the effects of climate change and that large portions of Amazonian protected areas include ‘disappearing climates’. In the face of these disappearing climates, the biggest determinant of many species’ extinction risks may be their ability to migrate through non-protected habitats.
Figure 1. Portions of officially designated protected areas of tropical South America that will (black) or will not (grey) have climate analogs under mean annual temperatures predicted for the 2050s according to the National Center for Atmospheric Research’s Community Climate System Model 4 (NCAR CCSM4) under Representative Concentration Pathways (RCPs) 2.6 (left hand panels, a and c) and 8.5 (right hand panels, b and d). Climate analogs are defined as having the same mean annual temperature ± 0.5 °C. In the top row (panels a and b), the search for climate analogs was extended to all connected or immediately adjacent (at ~5 km resolution) protected areas. In the bottom row (panels c and d), the search for climate analogs was restricted to within the same protected area. The percentage of protected area without future climate analogs under each scenario is indicated within each panel.
The Ecological Society of America recently held their 101st annual meeting in Fort Lauderdale, just north of Miami. Needless to say, the meeting’s location resulted in a strong contingent of ecologists from FIU and the Feeley Lab. Past and present lab members who showcased research included (in chronological order):
PhD candidate Timothy Perez who presented a poster on the patterns of community assembly in the genus Piper along an elevational gradient in Peru.
PhD candidate James Stroud gave two talks – the first was on the use of citizen science to conduct lizard surveys, while the second explored how unique competitive evolutionary histories may influence priority effects and the assemblage of novel anole communities.
Paulo Olivas, a past Feeley Lab post-doc and now a research associate at FIU, presented a talk entitled “Differential growth and physiological responses to water level and soil type in two dominant Everglades macrophyes, Cladium jamaicense and Muhlenbergia capilaris”.
Ken Feeley presented a synthesis of research
he has conducted with collaborators in Peru, Costa Rica, and Colombia that has investigated the up-slope shift in the distributions of tropical montane tree species in response to climate change.
Evan Rehm, a former Feeley Lab PhD student, presented research from his current post-doctoral position at Colorado State University, where he is working with collaborators to investigate how the loss of native avifauna can have cascading effects on the forest community. Evan’s talk discussed how to determine the seed dispersal services of avian frugivores to guide rewilding efforts on tropical islands.
Follow the links for each respective presenter to learn more about their research.
Below is a copy of recent commentary that I published in Frontiers of Ecology and Evolution based on the article by ter Steege et al on “Estimating the global conservation status of more than 15,000 Amazonian tree species“.
Amazonian forests provide ecosystem services that are critical at the planetary scale. Unfortunately, human land use threatens to drive many rainforest species to extinction. In a recent study, ter Steege et al. (2015) provide valuable insight into the threats that current and future deforestation potentially pose for Amazonian tree species. In any such large-scale analysis dealing with thousands of poorly-known species, there are clearly going to be many assumptions and possible sources of uncertainty. Here, I highlight two major assumptions used by ter Steege et al. (2015) to simplify their analyses—namely in the handling of widespread species and rare species. These assumptions have the potential to strongly influence predictions of how many and which species are at risk of being lost to deforestation over the coming decades.
Some tree species are likely to be endemic to the lowland Amazon; however, there are also certain to be many species that have ranges extending to higher elevations, different ecoregions, or even different continents. While ter Steege et al. perfunctorily acknowledge (in their online Supplemental Material) the potential problems caused by widespread tree species with geographic ranges extending beyond the defined Amazonian study area, they make no attempt to quantify how pervasive of a problem this may be or to account for it in any of their analyses. Rather, ter Steege et al. assume that rates and patterns of deforestation outside the Amazon mirror those occurring inside the Amazon. This goes against the core proposition of the study that spatial patterns of species’ distributions, population densities, and the rates of deforestation, all combine in determining the degree to which species are threatened by habitat loss.
To get a sense of how many species may have ranges extending beyond the Amazon, I mapped the locations where Amazonian tree species are known to occur based on their herbarium collections records. More specifically, I downloaded all georeferenced occurrence records available through the Global Biodiversity Information Facility (GBIF; http://www.gbif.org/) for the nearly 5000 Amazonian tree species occurring in the Amazon Tree Diversity Network’s (ATDN;http://atdn.myspecies.info/) forest plots and queried how many of these “common” species have recorded occurrences outside of the Amazon. I found that the vast majority (81%) of species have ≥1 occurrence outside the defined study region, one-fourth of the species have ≥50% of their occurrences outside the study region, and one-tenth of species have >90% of their occurrences outside the study region. Even if these extra-Amazonian populations are in some cases cryptic species, it is clear that many, if not most, Amazonian tree species are not actually endemic to the Amazon. For at least these widespread species, the data and methods employed by ter Steege et al. (2015) are insufficient to accurately estimate their true “global conservation status.”
In the case of rare species, there are believed to be ~11,000 Amazonian tree species (i.e., ~2/3 of total Amazon tree diversity) that are too rare to occur in any of the ATDN’s networked inventory plots (ter Steege et al., 2013). ter Steege et al. (2013, 2015) estimated the population sizes of these rare species based on an extrapolation of a rank-abundance curve created for the common species that do occur in their plots. ter Steege et al. (2015) then estimated the range sizes for rare species by assuming a fixed relationship between population size and range size. This methods explicitly disregards the different ways that species can be rare (i.e., the classic “7 forms of rarity”;Rabinowitz, 1981) by assuming that all rare species have small geographic ranges and that no rare species have large, low-density ranges. It is difficult to test this assumption due to the inherent relationship between a species’ density and its detection probability. However, it is easy to imagine that there may exist widespread species that occur at such low densities that they are effectively “invisible” to current census techniques—especially considering that the ATDN’s plots include < 0.8 million of the nearly 400 billion trees that they estimate to be growing in the Amazon (i.e., a sampling intensity of 0.0002%; ter Steege et al., 2013, 2015). In some cases, the ATDN may get “lucky” and a widespread low-density species will occur as a singlet or small number of individuals within one of their plots. According to the methods of ter Steege et al. (2015), however, the ranges of all species occurring in only a single plot, regardless of the number of individuals, are truncated to an arbitrarily set area (e.g., < 444 km from the plot where it occurs). A clear priority for future research in tropical forests is to understand the true nature of rarity.
The handling of rare and widespread species by ter Steege et al. likely adds large uncertainties to the predicted global extinction risks of many individual species. However, it is still possible that the cumulative result, that between about 30 and 60% of Amazonian tree species are threatened with extinction due to deforestation, is valid. The same two concerns about widespread and rare species were raised in a response to a previous study by Hubbell et al. (2008) that estimated the extinction risks posed by Amazonian deforestation (Feeley and Silman, 2008). A subsequent analyses byFeeley and Silman (2009) was then attempted with the explicit goal of at least partially bypassing these assumptions through the use of occurrence records, habitat maps and estimates of deforestation rates outside the Amazon (at the same time introducing other assumptions and possible sources of errors). Feeley and Silman (2009) predicted that Amazonian plant species will lose an average of 17 or 30% percent of their ranges by 2050 under Increased-Governance or Business-As-Usual models of deforestation—estimates that are strikingly similar to the new loss rates predicted by ter Steege et al. (ter Steege et al. predict that the population sizes of common Amazonian tree species will decrease by an average of 11 or 35%). In other words, while the data, methods, assumptions, and limitations differed greatly between studies, the final predictions were accordant. If nothing else, these studies all indicate that very high numbers of Amazonian species are already, or soon will be, threatened by deforestation. Add in the largely-unexplored effects of other human disturbances such as climate change, fire, forest degradation and defaunation (Peres et al., 2010), and it is clear that no matter what the underlying assumptions, the Amazon’s future is very dire indeed.
Evan Rehm, a former graduate student with FIU Department of Biology and ICTB (currently a postdoc at Colorado State University), and Dr. Kenneth Feeley have published a new article in the open-access journal Frontiers of Biogeography. The article is entitled “Many species risk mountaintop extinctions long before they reach the top“. In their article, Rehm and Feeley discuss the importance of ecotones, such as the alpline treeline, in setting current and future species’ distributions. They highlight the fact that many species’ range boudaries are set by ecotones and that these ecotones may not shift concurrently with climate change – potentially resulting in rapid range compressions and elevated extinction risks.