We can all imagine that climate change-driven migration of species will have global consequences. But what do the actual effects look like – and how do these feed back on ecology, climate and human societies?
Shown are 29 examples of ecosystems that are damaged due to climate-driven species migration or ‘biodiversity redistribution’. It’s a tip of an iceberg, as up to 40 percent of Earth’s biome surface will be forced to switch to another state – this century. Often ecosystem damage is accompanied by direct deterioration of human wellbeing – and sometimes species migration even activates positive climate feedbacks, further amplifying the initial warming. The effects though are not included in international climate and development policy goals.
This was assessed earlier this year in a metastudy by a group of no less than 41 biologists from 44 different research institutions who created an overview of available evidence of effects of warming-induced species migration on ecosystem health, human well-being and (in the form of amplifying feedbacks) the wider climate system.
The study concludes the effects of such a global ‘redistribution of biodiversity’ are widespread – yet largely unaccounted for in international development and climate adaptation goals.
It was published in Science on March 31 of this year. Lead author is Gretta Pecl of the Institute for Marine and Antarctic Studies of the University of Tasmania.
Climate-driven species migration
Climate change forces species to migrate to keep up with their respective climate zones. This migration takes place in three directions: uphill, poleward – and to deeper waters, as species try to find the cooler climatic conditions they evolved around.
As we’ve seen in earlier editions of our Climate Change & Anthropocene Extinction series this species climate migration happens at strongly variable speeds, depending on respective species adaptive capacities. Therefore ecosystems do not move as a whole, but get mixed up – and that’s where disturbance occurs, and damage.
To assess scale, don’t look at species – look at entire biomes
The magnitude of this species migration is best-illustrated by the scale of the underlying climate-driven biome migration. According to an earlier study by NASA scientists, up to 40 percent of Earth’s biomes could flip state over the course of the current century – as for instance rainforest switches to savanna or ‘boreal forest eats away Arctic tundra’.
Almost needless to say on a species level this process is messy, chaotic – and impossible to accurately predict – as climate-biodiversity models simply lack both species response mechanisms and data.
29 concrete examples of ecosystem damage, caused by climate migration
Now the authors of the Science publication of earlier this year list 29 clear-cut examples where climate change-driven migration of species (dubbed ‘biodiversity redistribution’) negatively impacts ecosystem health, possibly amplifying biodiversity loss.
“A case in point involves the expected effects of crabs invading the continental shelf habitat of Antarctic seafloor echinoderms and mollusks—species that have evolved in the absence of skeleton-crushing predators”
Often these ecosystem effects (as the top image shows) are also directly linked to other detrimental effects, including (20 examples presented) direct detrimental effects on human well-being and (4 cases) amplifying feedbacks on global climate warming – resulting from species migration.
Climate change-driven species migration activates feedbacks on ecosystem health, human wellbeing – and climate change, as illustrated in above model for the ‘taiga creep’ example.
Climate-driven species migrations might even fuel the initial warming
We already knew from other research that [just like ‘biodiversity saves biodiversity’ – positive rephrase] extinctions fuel more extinctions – and also more climate change. Yes, the feared positive climate feedbacks.
Next to broader mechanisms (marine phytoplankton ‘carbon pump’, albedo feedbacks from any vegetation change) the authors of the Science publication list four concrete examples of such feedbacks that can be triggered by climate-driven species migration – and all are positioned on boreal high latitudes. On of these is the projected disappearance of almost all Arctic tundra (shrub and moss) vegetation as it is replaced by northward migration of short pines that break snow cover, dramatically lowering albedo and thereby increasing solar heat absorption – amplifying Arctic summer warming.
Another clear example is pests of bark beetles that expand both their territory and numbers as boreal forest average winter temperatures rise. The large-scale tree die-off caused by such expanding pine beetle plagues can pose a significant positive climate feedback as it creates an imbalance in the local carbon cycle (already megatonnes of CO2, possibly escalating as warming continues). How to inhibit the pine beetle plague? It’s more than ‘stopping winter warming’ – it’s also improving forest biodiversity(!)
More uncertain is the role that the migration of plankton species may play. Through complex mechanisms the poleward migration may actually decrease the net spring algae bloom in the sub-polar North Atlantic – a region that is important for global CO2 sequestration.
Redistribution of plankton species [that can occur in three dimensions, let's not forget!] is also important because of their role in cloud formation as major producers of the DMS (dimethyl sulfide) aerosol. Overall, you’d especially hope for net plankton activity not to decrease…
The authors’ conclusion:
“The breadth and complexity of the issues associated with the global redistribution of species driven by changing climate is creating profound challenges, with species movements already affecting societies and regional economies from the tropics to polar regions. Despite mounting evidence for these impacts, current global goals, policies, and international agreements do not sufficiently consider species range – shifts in their formulation or targets. Enhanced awareness, supported by appropriate governance, will provide the best chance of minimizing negative consequences while maximizing opportunities arising from species movements – movements that with or without effective emission reduction will continue for the foreseeable future owing to the inertia in the climate system.”
Oh yes. Always good to end with that all-important reminder: climate inertia – the multiple decade time lag between emissions and warming. The main reason why the let’s first wait and see approach does not work. Especially since the mass migration towards the poles has already started – and not just on land, also in the oceans (and much faster there: on average 72 kilometres per decade).
That means there’s work to do on all levels and across the globe. And by now that should be more than ‘just’ climate mitigation as the Science publication clearly shows. We’ll need to work on ecosystem health directly too.
So let’s add ‘ecological adaptation policy’ to the UN climate lexicon? There is good reason, as we humans are not alone – and we humans cannot live without.
© Rolf Schuttenhelm | www.bitsofscience.org