What is the problem?

Figure 1. Shifts in suitable habitat for North American marine species, by region. Arrows indicate the average distance that the center of species’ suitable habitat shifted, not the actual locations.

What is a species range shift?

Species range shifts occur when there is a shift in distribution of a species beyond their previously recorded area of where it is usually found during its lifetime. The issue is very pertinent to marine ecosystems because 85% of animal phyla are found in marine habitats and 45% are exclusively marine. For example, climate change has had an effect on the direction of shifts in latitude and depth of more than 300 species in North America alone[1], some which may follow the trends in Figure 1. The shifts in the abundances of some species or groups of species in certain areas are likely to result in “winners” and “losers”[2][3][4]. Winners being able to remain stable or grow in abundance while expanding their distribution while losers face drops in population and distribution[3][4]. It is a complex problem with many things at play including, but not limited, to climate change, species interactions and fishing patterns[3][5][6].

Human actions responsible for shifting species ranges

The issue of shifting species ranges is a one that lives in tandem with that of climate change[7]. Their close linkage means they share a common set of human causes, primarily surrounding the excessive release of greenhouse gases over recent decades [8]. As is wildly discussed, current climate instability is a result of increased atmospheric carbon concentrations[9] due to the excessive burning of fossil fuels[1], resulting from increases in consumption patterns and the industrial revolution[8].

Map of global ocean surface temperatures.
Figure 2. Map displaying global ocean surface temperature gradients, showing gradual shift from warm equatorial waters (orange) at low latitudes to cold polar waters (purple) located at high latitudes.

Areas effected by shifting species ranges

Given the global extent of shifting climatic conditions, which are driving species range shifts[1], there are few locations on earth that will be exempt from this pervasive issue [10]. That being said, the impacts and their severities will not be evenly distributed across the globe[3]. As ocean temperatures warm[11], the world's warmest waters, located at low latitudes, will gradually become uninhabitable as species physiological limits are reached[12]. This means that species living in these equatorial ecosystems will be forced to higher latitudes in search of colder water[13]. High latitude, cold water regions will also suffer greatly from shifting species ranges, both directly - as thermal tolerance thresholds approach[1], forcing species to Northerly waters[12], and indirectly - as tropical species move into these cold water regions and create new competition, leading to community re-structuring[1]. Research done on the Northeast Continental shelf suggests that shelf ecosystems are experiencing warming at a faster rate than the global ocean, and consequently, are seeing large changes in species distributions to Northerly physiological limits[3].

How pervasive is the problem?

This problem pervades throughout all aspects of life on earth and affects every type of life and group of organisms. It affects both terrestrial and marine life in similar ways but for the purposes of this article the focus will remain on marine life. In various studies it has been shown that in marine range shifts species range's generally move poleward and this extends to many different species [2]. This also extends to different marine environments around the globe which have wide and varying effects on the ecosystems involved. Some may result in the destruction of entire ecosystems as some studies have shown, one example being the range shift of kelp species resulting in the loss of kelps in certain ecosystems, destroying them.[14]. Therefore range shifts are a pervasive problem which pertains to all levels and facets of marine life.

Ecosystem Impacts in British Columbia

Poleward Shifts

The poleward shift of marine fish and invertebrate ranges occurring in British Columbia’s marine systems, due to increasing ocean temperatures[3], are influencing these ecosystems through their reorganization of species assemblages and consequent shifts in species interactions [13].  Global surveys also showed this trend, with 75% of monitored species ranges shifting in the poleward direction[15]. These observed distribution shifts are driven by the relationship between species physiology, reproduction, and dispersal to temperature and patterns of ocean current [12].

Figure 3. The Pacific Little Neck Clam (Leukoma staminea), an important species in Coastal British Columbia's marine ecosystems.
Figure 4. Manila Clams (Venerupis philippinarum), native to Japan, invasive in British Columbian waters and showing Northward movement, resulting in competition with British Columbia's native Pacific Little Neck Clam.

Latitudinal Vulnerability

An important quality making British Columbian marine ecosystems particularly vulnerable to the impacts of species range shifts is its high latitude. Given the pattern of shifting species ranges to Northerly locations[12], an increased dominance of warmer-water species is being observed [10]. This shift in dominance is driven by the high tolerance of low latitude species to warm water temperatures[12], which favor their growth and trigger an acceleration in their reproductive success, allowing for their continued Northerly movement and domination [12].  Studies have observed this trend of increasing warm-water species dominance in invertebrate populations in the Northeast Pacific, and mollusk populations in the Northwest Pacific [10]

This idea of increased vulnerability of high latitude species and ecosystems, to warming ocean temperatures and species range shifts, is supported by extinction data recorded during end-Permian warming[16], which showed disproportionate extinction rates among high-latitude taxa, indicating that these species ran out of space possessing a habitable climate, and were consequently driven to extinction [16].  

Organismal & Community Impacts

British Columbia’s coastal ecosystems have seen the impact of shifting dominance of warm water species, through alterations of the natural trophic order, and consequent shifts in community structure [12]. An example of this has been observed with Manila Clams (Venerupis philippinarum), originally from Japan, whose Northerly population expansion in British Columbian Waters[17], has led to its competition with native species such as the Pacific Littleneck Clam (Leukoma staminea) [18]. It is highly likely that the increasing domination of the Manila Clam in British Columbia's warming waters, is tied to the low latitude of its origin (Japan, 32° N)[19], and its consequent tolerance to warmer ocean temperatures. The competitive impacts of warmer water species such as the Manila Clam, aren't restricted to the species with which they directly compete, such as the Pacific Littleneck Clam, but they also influence all predator, prey relationships within that system. A decline in Pacific Littleneck Clam populations, for example, would likely influence their many natural predators, such as: leafy hornmouth snails (Ceratostoma foliatum), moon snails (Euspira lewisii), Octopus (Enteroctopus dofleini), sea otters and crabs (Metacarcinus magister and Cancer productus) [20]. This example communicates the wide ecosystem re-organization resulting from expanding ranges of species, due to warming ocean temperatures.

Cold-Water Species Vulnerability

Other organisms seeing the greatest impacts of shifting species ranges are those best suited to live in cold water.  A unique characteristic that makes cold-water species particularly vulnerable to shifting species ranges is their narrower temperature preference range relative to warm water species[12]. In tandem with this, is the observed pattern that fish species circumvent living in habitats at the edge of their temperature tolerance [12]. This narrow tolerance range makes cold-water species more sensitive to ocean warming, giving them a selective disadvantage against the many warm-water species moving upwards into British Columbia’s marine ecosystems.  Additionally, the reality that increasing global temperatures are making cold water areas less abundant, means that cold-water species have a significantly smaller range of area that could support their relocation.  

British Columbian species such as pink salmon (Oncorhynchus gorbuscha), chum salmon (O. keta), coho salmon (O. kisutch) and capelin (Mallotus villosus) are some of these cold-water species being most heavily impacted within BC’s marine ecosystems[12] .

What is the extent of the problem?

What are the measurable ecosystem changes that have occurred?

There are many examples of species range shifts that have occurred as a result of changes in climate. In an annual review of relevant literature[2] it was shown by many studies that various species saw an increase in their ranges poleward compared to their historical ranges. The review touched upon three different species from three separate studies which all concluded that these species had experienced an increase in their Latitudinal range. This study found that across those three species, American Lobster, Humboldt Squid and the cushion star, their ranges almost always moved into cooler waters more suitable for them. These changes have been associated to warming ocean temperatures and organismal responses to them by seeking out more favorable thermal environments[2].

Figure 5. Predicted changes in two in the suitable habitat for the kelp species Sargassum horneri in the East and South China sea over time for two standardized climate scenarios.[21]

What is the present status compared to the past?

While there are currently more efforts to combat species range shifts across both marine and terrestrial environments across the world. Progress is being made on some fronts, that being reintroduction of species to native environments, and elimination of invasive species, but there are still large-scale environmental changes, ie. Global warming, ocean acidification, and human factors, which means this is a pervasive and growing problem as was described in a study that reviewed species range shifts from across the world.[8] The general conclusion from this study is that compared to the past species ranges' are shifting at a more aggressive rate and this is mostly due to anthropogenic factors, specifically in regards to climate.

Figure 6. Durvillaea antarctica a species of kelp endemic to the southern oceans the range of which is increasing due to warming oceans and melting sea ice.[22]

One example of a group of organisms currently going through a range shift are kelps and the larger species of brown algae. Compared to historical data there is an increase in the speed of brown algal, specifically kelp, range shifts [23]. This can be a devastating range shift for some ecosystems since many kelps are keystone species and are required for many types of ecosystems to exist. It is important to note however that this also includes the introduction of kelp species into new habitats as their ranges expand poleward. For example, certain kelp species have begun to expand their areas in the Antarctic, as warming temperatures and the melting of Sea Ice lead to new suitable habitat for kelps in the region [22].

What is the prognosis for the future if we continue on our current trajectory?

There are a few measurable changes in species range shifts that are projected to occur along the current trajectory. One such example is the changing distribution of pelagic fish species. One study that analyzed this examined 28 species of pelagic fish native to the West Coast of British Columbia, and their latitudinal range [1]. This study found that the general range of these species was shifting north at an average rate of 30.1 ± 2.34 (S.E.) km decade­-1. This is a measurement of the center of species distribution and its shift northwards over time, which is an example of species range shift. In this study this measurement is based off a model of predicted ocean conditions as the climate changes over time. Studies have found a similar trend of poleward range shifts in Algae as well. A study done on algae in China predicted the changes in the habitable zone for a species of brown algae over time if the changes in ocean temperature seen now carry on[21].

Overall, the current prognosis should this problem persist based on the research is that without major intervention in the mitigation of anthropogenic factors such as overfishing and climate change, species range shifts will only become more aggressive over time[8].

Given the impact, what are the solutions?

Global scale solutions

Climate change is the main driver in species range shifts, so reducing greenhouse gas emissions would help solve the issue[24].  Switching to clean energy resources, reducing CO₂ emissions, and halting deforestation are all steps the world should be taking to reduce emissions[25]. However according to IPCC, given the current state, even if humans stopped all emissions immediately, global temperatures would still increase until reaching equilibrium with the new gas concentrations centuries later because of the long lifetimes of greenhouse gases and the ocean’s ability to absorb heat[26]. Additional studies bring up land use as something equally influential in latitudinal and elevational range shifts, hence studies should be less focused on climate change only[27]. Habitat connectivity and landscapes affect whether species can shift their range, so removing any anthropogenic barriers in the way of species distribution and changing our land use should be investigated[27].

Local scale solutions

Figure 7. Bladder wrack (fucus vesiculosus) top-left where it is home to many marine organisms and under the effect of rapid ocean warming.


Using models to predict species range shifts and conducting more research on species interactions are important in determining smaller scale solutions[2] [12]. As mentioned above, warm-water species are displacing or replacing cold-water species[5]. In addition, highly mobile species such as pelagic fish are observed to be shifting poleward[1]. This could result in a desynchronization in species composition because the sessile organisms cannot displace themselves to a more favourable area[28]. The bladder wrack (Fig. 7) for example, cannot shift its range fast enough to escape the rapid warming in the Baltic Sea. This combined with habitat fragmentation and eutrophication would drive bladder wrack numbers down and would endanger organisms such as fish, other algae, and many invertebrates that rely on the canopy-forming seaweed for habitat[29]. By predicting the possible species compositions using models, research could be done on the interactions between them to identify geographic priorities where desynchronization in species composition could be an urgent issue under global climate change[2].

Figure 8. Many components come together to reduce genetic diversity, making smaller populations at risk of getting even smaller until extinction.

Genetic variation

Species that cannot shift their range at the pace of the changing environment must persist in the new environmental conditions or perish[30][28]. From a local perspective, increasing genetic variation and the speed of integration into the species would be crucial[14][29]. This has been considered by introducing greater genetic variation through individuals from better adapted populations to the given conditions[4]. For example, seeding kelps in areas of dwindling kelp populations such as in the Gulf of St. Lawrence[14]. Another solution is to increase the habitat to increase population size. This would lessen the effects of genetic drift, inbreeding depression and environmental random chance events favouring a population over another. These effects would be fatal to small populations (Fig. 8) or partial populations moving into a new habitat[30].

Figure 9. Atlantic cod is one of the key commercial fishes on the watch for range shifts.


From a human-centric view, fisheries now need to move their fishing areas mostly poleward to follow the movement of species[1][31] such as to follow the continued northward shift of Atlantic cod (Fig. 9) for colder spawning areas[6]. However, some fisheries are experiencing a lag in responses or cannot move as quickly as the species ranges are shifting. To solve this issue some fisheries are expanding or changing the list of species they are fishing for[31][6]. Doing so could prolong the existence of a fishery and allow them to transition to a new species, but needing to find, or even possibly create a new market for a new commercial fish species adds another layer to the situation. It could also run the risk of overfishing the population if it is done without considering what competing companies are fishing[31].


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