- Oct 2018
Assessments of climate change on species’ ranges need to account for observations across the full extent of species’ latitudinal and thermal limits and explicitly test for interactions with other global change drivers.
This type of assessment is important for determining threat statuses for species, such as International Union for Conservation of Nature (IUCN) Red List of Threatened Species (see here to look at an assessment done for the Rusty Patched Bumbebee).
These assessments are also important for planning conservation actions as part of initiatives like the U.S. Department of Agriculture and Environmental Protection Agency's Pollinator Health Task Force, which was established to "[promote] the health of honey bees and other pollinators (including birds, bats, butterflies, and insects)".
Regions where the speed and variability of climate change are lower than in the surrounding area. These climate refugia have the potential to act as "safe havens" where species can retreat to and persist as the climate changes.
A similar concept is the glacial refugia used by many species during the last ice age. Visit the Encyclopedia of Earth for more information on refugia.
Thermoregulation is the process through which animals increase or decrease their body temperature. Thermoregulation can be done physiologically (e.g. by sweating to cool down during a hot day), or can be done behaviorally (e.g. by taking shelter in the shade during the hottest parts of the day).
Common examples of behavioral thermoregulation are lizards or butterflies basking in the sun. (Photo courtesy Discover Wildlife)
One of eight "realms" that divide Earth's surface. It comprises Europe, North Africa, Asia (north of the Himalayas), and the northern and central Arabian Peninsula. The Palearctic is primarily boreal/subarctic and temperate in climate.
Drawing on comprehensive range data, bumblebee species show opposite range responses across continents relative to most terrestrial assemblages (4): rapid losses from the south and lagging range expansions in the north
As we can see from Figure 1, the northern/cold end of species' range limits are not shifting, whereas the southern end of the range have shifted northwards.
Neonicotinoid effects known from individual and colony levels certainly contribute to pollinator declines and could degrade local pollination services.
This was shown again in some recent 2017 studies, find out more in this Science Perspectives piece.
In contrast to expectations and responses known from other taxa (4), there has been no change in the northern limits of bumblebee distributions in North America or Europe (Fig. 1A). Despite substantial warming (~ +2.5°C), bumblebee species have also failed to track warming along their cool thermal limits on both continents (Fig. 1B and Table 1).
As we can see in Figure 1A, there was no shift in northern range limit for species (on average), in North America or Europe. As the authors point out, this is a surprising result because other marine and terrestrial ectotherms have been observed moving further north in recent years.
This is also surprising because we can see in Figure 1B that species' cool range limits have warmed by about 2.5°C.
Refers to the thoroughness of people having surveyed a region for species observations. Certain regions and times are more surveyed than others for often mundane reasons, such as accessibility. For example: If a flood washes out the road to a popular park, the park will likely not be searched as often until the road is rebuilt.
These differences in sampling effort between regions and time periods can create trends within the data that are not real. For instance, in the aforementioned example, after the road is washed out and sampling effort decreases, it would appear as if there are less organisms in the park, when in reality there could be the same number of organisms and just fewer people to record them.
In this study, the authors account for differences in sampling intensity by only including species in their study if they had over 100 observations in a baseline time period, and over 30 observations in each other time period.
Describes the evolutionary relationships among organisms (i.e. how related is one organism to another), based off of similarities and differences in physical or genetic characteristics.
Visit here for more information on what phylogenetic trees are and how scientists build them, by Khan Academy.
phylogenetic generalized least-squares models
Tests for a relationship between two or more variables, while accounting for phylogeny (i.e. the fact that some species, or lineages, are more closely related than others).
"Regular" models, such as Generalized least-squares models, or Ordinary least-squares models, also test for a relationship between two or more variables, but these tests assume that variables and species are independent (i.e. are all equally related). When this assumption is violated, the test results can be biased.
We measured differences in species’ northern and southern range limits, the warmest or coolest temperatures occupied, and their mean elevations in three periods (1975 to 1986, 1987 to 1998, and 1999 to 2010) (figs. S2 to S4) relative to a baseline period (1901 to 1974)
To test whether climate change has impacted species ranges, the authors had to measure, for each species, the latitudes of the northern and southern range limits (and the distance between these), the warmest and coolest temperature the species were observed, and the mean elevation of the species.
These measurements are based on the average of the five most relevant species observations in each case. For example, to find the northern range limit, the authors took the average of the five northernmost observations of the species, while to find the coolest temperatures within the species' range, they took the average of the five coolest points that the species was observed at. This helps avoid skewed results from a signal sighting.
Check out the Supplemental Materials for more information on how the authors took all their measurements.
"Georeferenced" means that we know where a species observation was made. This means that we have the latitudinal and longitudinal coordinates for the location where someone found a particular species. It's not just a description of the place, like "third mountain from the left, in Colorado," because that doesn't help us know where a species was found very reliably. These days, it's a lot easier to figure out those coordinates, because most smartphones include GPS that records exactly where something is found. This is the same feature that lets a user track where they are on a map, use Pokémon Go to find an elusive Pokémon, and so on. But instead of finding virtual animals, we can record where the real ones are found. But records from a hundred years ago (obviously) didn't get stored using smartphones, so there's a lot of manual work needed to figure out where those records came from.
contribute more to these services than bumblebees (Bombus)
Visit the Bumblebee Conservation Trust for more info on what makes bumblebees such great pollinators.
Common land-uses include: agriculture, urban space, or wilderness. An intensification of a land-use means that the human influence on the land has increased, but without changing the type of land-use. Typically this includes an increased output of pollutants.
For example, while a pesticide-heavy, monocultured farm field has the same land-use as a pesticide-free organic farm, the intensity of land-use at the monocultured farm would be greater, even if the farms were the same size.
- Sep 2018
Not all bees are honeybees! There are actually about 25,000 different species of bees, and the European Honeybee is just one. Bumblebees (genus Bombus) can be distinguished by their fuzzy abdomens and generally larger size.
Check out this infographic from Gould (2015) showing the different families of bees, and "bee hotspots" around the world.
Mean elevations among northern species in Europe and North America shifted lower.
Interestingly, northern species shifted lower down the mountains—the opposite of southern species!
Also known as assisted colonization or facilitated colonization, is the act of deliberately moving a species to a different habitat, that the species would have eventually occupied given enough time or the removal of another barrier to its natural dispersal. This is in contrast to other types of assisted migrations or species introductions, where species are moved to completely new regions that they would likely never see without human intervention (e.g. the introduction of Cane Toads to Australia, or mongoose in Hawaii).
In this instance, the authors suggest that controlled and carefully managed relocations of bumblebee colonies further north could help these species to track climate change and avoid range compressions.
No study has yet evaluated climate change impacts across the latitudinal and thermal limits of such a large species assemblage spanning two continents.
Here, the authors are showing that their research is something that no scientist had known or been able to do before. The purpose of this sentence is to show why an analysis like the one in this research might be important and tell us something that we had not known previously.
Indicates a change in where species are found. There are two ways this can happen. First, a species can move into a new place where it never used to be found. Second, a species can disappear (or go locally extinct) from a place where it used to be found.
Status and Trends of European Pollinators Collaborative Project
The Status and Trends of European Pollinators (STEP) Collaborative Project, is a multinational European initiative to "assess the current status and trends of pollinators in Europe, quantify the relative importance of various drivers and impacts of change, identify relevant mitigation strategies and policy instruments, and disseminate this to a wide range of stakeholders."
See here for more info.
The precise cause of an observed trend.
For example, if the trend we observe is a door opening and closing by itself, the mechanism causing this trend may be the circulation of air in the hallway adjoining the door, or the mischievous actions of a sibling using a long line of transparent fishing line.
In this study, the observed trend is the lags in range responses at species’ northern or cool thermal limits. Potential mechanisms could include a lack of host-plants in these newly-accessible regions at the northern thermal limit, or a competitor species that currently occupies this space.
Species with southern geographical ranges retreated to higher elevations across Europe and North America (Table 1 and Fig. 2), consistent with observations of range losses from their southern range limits.
As we can see from Figure 2, species with ranges further south moved to occupy higher elevation in recent years.
The plural of taxon, which refers to a taxonomic group of any rank (species, families, classes, etc.).
Animals that depend on external sources of body heat to control their temperature. Other examples include reptiles (excluding birds), amphibians, and fish.
applications accounted for changes in bumblebee species’ range or thermal limits (table S3)
Without also testing competing theories (land-use and pesticides), the authors would not be able to say how important the effects of climate change were in influencing range limits. Remember that the scientific method does not allow us to definitively prove a theory, only add to the evidence that one hypothesis is more likely than the alternatives.
We investigated whether land use affected these results. Finally, we used high-resolution pesticide application data available in the United States after 1991 to investigate whether total pesticide or
Because climate change is not the only possible explanation for changes in species' latitudinal and thermal range limits, the authors also tested other competing theories, like land-use changes and pesticides.
A class of insecticides designed to affect the central nervous system of insects, causing paralysis and death. They are also systemic insecticides, meaning they are absorbed into every cell of a plant, and making every part poisonous. Pesticides, and neonicotinoids in particular, have been implicated as a possible reason for pollinator declines.
Watch Prof. Richard Pywell (unrelated to this study) explain what neonicotinoids are and how they may be affecting pollinators here.
A group, or community, of species.
Biological effects of climate change threaten many species
This has been shown by studies time and time again, and the United Nations' Convention on Biological Diversity (CBD) lists climate change as one of the major threats to the world's biodiversity, along with habitat loss.
Read more about the value of biodiversity, threats to biodiversity, and the coordinated actions the CBD is taking with governments around the world to combat biodiversity loss on the CBD website.
- Aug 2017
As with failures to expand northward or into cooler areas, land-use changes do not relate to range losses from bumblebee species’ southern or warm thermal limits
We can see this in Table S3 in the Supplementary Materials.
model selection includes a small continental effect; intercept for Europe, 1459 m (366 SE); North America, 1074 m (340 SE) (Fig. 2)]. Europe’s mountainous areas are oriented predominantly east-west, potentially inducing more pronounced upslope shifts.
A continental effect indicates that the shifts in elevation are predictably different depending which continent the species is on.
Positioning of the mountains could cause this.
bumblebee species’ range losses from their historical southern limits have been pronounced in both Europe and North America, with losses growing to ~300 km in southern areas on both continents (Fig. 1C).
As we can see in Figure 1C, species in southern areas have seen their southern range limits shift by as much as 300 km on average.
southern range limits should have remained stable with increasing temperatures along species’ warm thermal limits
As mentioned in the previous paragraph, most species have not experienced range declines in the southern parts of their ranges.
Spatially detailed, annual pesticide measurements, including neonicotinoid insecticides, were available for the United States after 1991.
The authors used these to measure the mean annual exposure of species to pesticides. See the Supplementary Materials for more information.
These failures to track climate change occur in parallel in regions that differ in their intensities of human land use (e.g., Canada and northern Europe), which had no direct or interaction-based effect in any statistical model (Table 1)
Canada and northern Europe have very different histories of land-use. If land-use were an important factor behind declines in bumblebee ranges, than there likely would have been a difference in bumblebees' ability to track climate change between North America and Europe.
The authors did not see this, and conclude that land-use is likely not an important factor driving these range declines.
These locally important effects do not “scale up” to explain cross-continental shifts along bumblebee species’ thermal or latitudinal limits. The timing of climate change–related shifts among bumblebee species underscores this observation: Range losses from species’ southern limits and failures to track warming conditions began before widespread use of neonicotinoid pesticides (figs. S2 and S3)
The authors conclude that while neonicotinoids and other pesticides do kill bumblebees, they are likely not responsible for the large-scale declines in range sizes that are observed.
Observed losses from species’ southern or warm boundaries in Europe and North America, and associated phylogenetic signals, are consistent with ancestral limitations of bumblebees’ warm thermal tolerances and evolutionary origins
Bumblebees evolved in cool, temperate conditions, and did not need to evolve tolerances to high temperatures. Considering this, it's not surprising that they are dying out from the regions of their ranges that reach the hottest temperatures.
If species expanded their northern range limits to track recent warming, their ranges should show positive (northward) latitudinal shifts, but cool thermal limits should be stable through time.
Here the authors outline one of their main hypotheses (species will expand their northern range limits to track climate change), and the subsequent prediction.
All data and supporting scripts are available from Dryad Digital Repository: doi:10.5061/dryad.gf774.
Warming-related extreme events
Extreme (weather) events such as hurricanes, tornadoes, and floods, and particularly warming-related extreme weather events, such as droughts and heatwaves, are expected to become more frequent as a result of climate change.
Visit here for more information on extreme weather events and their relation to climate change, courtesy of the 2014 U.S. Global Change Research Program.
Global Biodiversity Information Facility
The Global Biodiversity Information Facility (GBIF), is a free, open-access platform for collecting and sharing data on species observations.
Visit GBIF here.
Bumblebees of North America
Bumblebees of North America is a comprehensive guide to North American bumblebees.
See here to preview the guide yourself.