7) This is an emergency!

A novel driver of species extinction in the 21st century is climate change. Combined with land-use change, extinctions are 50 to10,000 times the background rate (Figure 1). Climate change directly impacts ecosystem functions as temperatures rise and land becomes drier (eg. Australian fires). For global warming of 0.8°C to 1.7°C, projected vertebrate extinctions range from 11-34%, compared to 33-58% for >2.0°C warming. Species have responded and will respond in 3 ways: migration, adaptation or extinction. Let us explore these responses through aquatic, ancient and arctic species.

Definition: Climate change is a long term shift in global and regional weather patterns.

Figure 1. Comparison of recent and distant past extinction rates with rates at which species are “committed to extinction” during the 21st century (Pereira et al, 2010)

The range of extinctions reflects the inherent uncertainty of forecasting the future. Hence, scientists have predicted 'committed extinctions' for minimal and maximal climate warming scenarios. Species who escaped the first anthropogenic armageddon (land-use change), will have to conquer the second (climate change).

Swimming to safety (migration)

Ever wondered if life under the sea is better? Compared to terrestrial troops, lower extinctions are forecasted for aquatic allies because of their greater migratory freedom, ideally, away from inhospitable ecosystems. Imagine having a universal passport. As climate warms, scientists anticipate a polewards shift of marine organisms (Figure 2), some residents of the North Sea have already evacuated! Pelagic species will be the first to migrate compared to their demersal pals who live beneath them, closer to the seabed. Similarly, smaller species with faster life cycles are quicker to pack up their bags and migrate. Evident in the borealisation of fish migrating to the Arctic.

The plight of endemic species in enclosed seas is gloomier as harsh waters will force adaptation or extinction. You would think visas are redundant for sessile species (coral) who are literally stuck in their birthplace. However, young corals are fairly mobile with a push from ocean currents!

Figure 2. Projected rate of range shifts in marine organisms caused by climate change from 2005 to 2050 (52, 63). (A) Latitudinal shift of demersal species (excluding areas >2000 m in depth because of undersampling of the deep-sea region). (B) Latitudinal shift of pelagic species. The projections are based on bioclimatic envelope models for 1066 species of fish and invertebrates, under IPCC SRES A1B (Pereira et al, 2010)

A 1°C increase in sea surface temperature for more than 8 weeks can lead to severe coral bleaching.

Ancient, aquatic, adaptive

Thriving in the ocean for over half a million years, coral ecosystems have been early responders to climate change. Around 30% are already damaged and ~60% could be lost by 2030. Even the most thermal tolerant corals are being severely tested.

Image source: BBC America

Bleaching is one of the many challenges caused by climate change. Sea-level rise causes sedimentation run-off that smothers near land corals. Increased storm frequency and intensity can cause destruction. Changes in ocean currents affect accessibility to food and dispersal of coral larvae. Ocean acidification caused by increased uptake of CO2 damages growth. These combined forces are driving reefs towards the tipping point of functional collapse. Under such turbulence, corals face the ultimate test of resilience.

The idea that corals need longer time frames to evolve and adapt to changing environments is based on their long-life history. Whilst high levels of asexual reproduction and overlapping generations can damper evolution in many corals, others can adapt. The variation in rates of gene flow between corals is vast, therefore, corals with high levels of gene flow can migrate in response to climate change. Others will eventually die out, theoretically, creating coral ecosystems that are genetically adapted to acidic, warmer oceans. However, with all biological systems, uncertainty rests with complexity. The ability to migrate and adapt is limited to interconnected populations. Those around islands (Bermuda) or archipelagos (Hawaii) are isolated with limited chances of experiencing genetic flow.

Why ice is nice

The Arctic is the region experiencing the highest rates of warming (Figure 3), if you're wondering how this affects you beyond sea-level rise, enter Albedo. The albedo effect creates a synergistic loop between ice melt and rising temperatures. Without ice and snow to reflect the sun's energy into space, the rocks and oceans absorb more energy; accelerating global warming. More importantly, the loss of sea-ice threatens several species with extinction.

Figure 3. Amplification of temperature rise in the Arctic in comparison to global temperature change from 1860 to 2020 (The Conversation, 2019)

Here are 11 species on the front line of climate change, click here to read their stories.

Polar Bears

Beluga Whale

Saimaa Ringed Seal

Musk Ox

Walrus

Lemming

Arctic Fox

Narwhal

Reindeer

Orca

Image sources: Pinterest and animals.net

A polar bear weighs up to 800kg! They need the ice to hunt for seals and find mates. 'Business as usual' sees a 30% loss of the polar bear population by 2050. Controlling for environmental risks, mammals like the Arctic dwellers are most vulnerable to extinction due to a higher body mass and low reproduction rates,. Now we have dropped in the pressure of climate change, their chances of survival are next to nothing unless we reduce our human footprint and increase conservation efforts.

Geography matters

I need not be a Geographer to state this. Species ranges' influence their capacity to respond to climate change. The non-domesticated need to find food, avoid prey, and now, adapt to mother nature's rising fever. As temperatures rise, some species gravitate polewards (migration), others choose higher elevations. However, those already on the mountaintops cannot go higher. Migration comes with species fragmentation and a potential reduction in geographical range.

Species who cannot: shift their ranges, inhabit narrow climate niches, adapt their phenology, physiology or behaviour, will be the first to go extinct. On the other hand, large range species with greater genetic diversity are more resilient.

Researchers suggest that evolutionary processes and adaptations are not an alternative to range movements but operate synergistically to the dynamics of range‐shift. The trio of migration, adaptation and evolution is nature's version of The Deathly Hallows sign.

47% of the proportion of terrestrial flightless mammals and 23% of threatened birds have already been impacted by climate change. The majority of terrestrial species ranges are projected to shrink profoundly with 1.5 to 2°C of global warming (IPBES, 2019)

Indeed, it's survival of the fittest, not bittiest.

Uncertain futures

Future projections of species response to climate change are based on models, with every model, comes a degree of uncertainty. The Inter-Sectoral Impact Model Inter-comparison Project (ISI-MIP), provides impact assessments, that scientists can use to inform biodiversity conservation. Further research is needed on the nexus between climate change and intrinsic biological traits (geographic range, body size, reproductive rate) that determine how species respond to rising anthropogenic activity. In the face of uncertainty - diversity is the key to resilience.

We know definitively, the pressure upon wildlife from the human footprint (see post 5) is further exacerbated by climate change. Luckily, actions are being taken to address climate change and pressure systemic change.

If there is anything I've learnt from 2020, it's that complacency is not enough, my role matters and so does yours. I finally plucked up the courage to join a movement. I found this resource helpful towards acting now!

Next week, we explore the vein and rooted response.

Thanks for reading, J x