• Vikki Lawman

Ecosystems on the edge of a warming World

From shifting weather patterns and rising sea levels to catastrophic floods and threatened food production, climate change is one of the defining issues of our time. The impacts of climate change are global in scope and unprecedented in scale. Sea level rises, extremes in weather patterns and the melting of ice caps are just some of the consequences. The gradual warming of the Earth along with human interactions has had and will continue to have devastating effects on the different global ecosystems if more action isn’t taken.


Ecosystems or biomes (large scale ecosystems), are made up of living organisms and non-living components all interacting together in a shared environment. The major biomes on Earth include forests, deserts, polar regions, grasslands and aquatic, either marine or freshwater.


The living organisms are known as the biotic components of an ecosystem and include plants, trees, micro-organisms and animals. These interact with other physical non-living components such as the sun light, climate, geology and soils known as abiotic components. Chemical components such as oxygen (O2) or nutrients are also abiotic components of an ecosystem. As the Earth succumbs to global warming the conditions of these ecosystems are changing but how long will it be until such a time that these ecosystems become unbalanced and collapse? Can we save them? There is a tipping point and scientists have been trying to predict what this might be and how long it will be until such an event is likely to happen.

Previous reports and investigations have often focused on estimating the damage of climate change if the average temperatures on Earth were to rise by 2°C. However, a report from the IPCC shows that many of the adverse impacts of climate change will come at the 1.5°C mark – a scary thought! With clear benefits to people and natural ecosystems, the report found that limiting global warming to 1.5°C compared to 2°C could go hand in hand with ensuring a more sustainable and equitable society. (IPCC, 2018). For instance, by 2100, global sea level rise would be 10 cm lower with global warming of 1.5°C compared with 2°C. The likelihood of an Arctic Ocean free of sea ice in summer would be once per century with global warming of 1.5°C, compared with at least once per decade with 2°C. Coral reefs would decline by 70-90 percent with global warming of 1.5°C, whereas virtually all (> 99 percent) would be lost with 2°C. (IPCC, 2018).

The report also found that global net human-caused emissions of carbon dioxide (CO2) would need to fall by about 45 percent from 2010 levels by 2030, reaching ‘net zero’ around 2050. This means that any remaining emissions would need to be balanced by removing CO2 from the air. (IPCC, 2018).

Of course, the effects of climate change are not just the only threat to the survival of the Earths ecosystems. Overexploitation of resources for human gains such as deforestation, overfishing and effects of plastic pollution can all contribute to a shift in the state of an ecosystem.


Let’s take a trip around the globe and highlight just some characteristics and threats to the main ecosystems on Earth and what can potentially be done to protect them:


Forests



Tropical rainforests, often referred to as the lungs of the Earth, are located close to the Equator where the climate is hot and humid and is one of the most biodiverse places on Earth. The deciduous forests are found in temperate Europe and in the USA. These trees respond to the seasons and lose their leaves in winter every year and thrive in mild and wet conditions. Forests are under constant threat from climate change, fire, disease and human exploitation - Logged for exotic woods and cleared for palm oil plantations.

Forests provide critical refuges for terrestrial biodiversity, are a central component of the Earth’s biochemical systems and are a source of ecosystem services that are essential for human wellbeing. (Shvidenko et al., 2007). Whilst forests can help combat climate change, they are also highly vulnerable to changing climatic conditions. The climate at a given location determines the type of forest that can become established. When climate conditions change, forests must adapt. However, the adaptation process usually requires more time than the changing climate conditions allow. This often results in a loss of forests, their biodiversity, and their ability to mitigate the impacts of climate change.

The effects of climate change have also been shown to have effects on forest diseases and pathogens resulting in tree mortality. Elevated CO2 was shown to increase host resistance to two forest diseases in the southern USA (Runion et al., 2010). Because abiotic factors such as temperature and moisture affect host susceptibility to pathogens and pathogen growth, reproduction and infection, changes in interactions between biotic diseases and abiotic stressors may represent the most substantial drivers of disease outbreaks. (Sturrock et al. 2011).

This doesn’t mean that we should let the forests fall victim time and time again. Sustainable forest management can contribute towards strengthening the resilience of forests, enabling them to adapt to climate change impacts as well as natural disasters and disturbances. Education can also go a long way to empowering people and local communities to make better and more sustainable decisions for the future of the forest.


Grasslands



The grassland biome includes terrestrial habitats that are dominated by grasses and have relatively few large trees or shrubs. The 3 main types of grasslands are tropical grasslands (savannas), temperate grasslands and steppe grasslands. Wetlands are also a very important part of grassland ecology, home to an array of many bird species and wildlife. Protecting and conserving them are critical for the health of our natural world.

Sadly, one of the main threats to grasslands is habitat loss which can be caused by anthropogenic actions such as unsuitable agricultural practices, over grazing and crop clearing. The relatively flat terrain of grasslands also increases their vulnerability to climate change impacts, because habitats and species must migrate long distances to compensate for temperature shifts. Extremes in weather such as drought can have lasting implications for the vegetation.


A snapshot of the Earth’s plant productivity in 2003 shows regions of increased productivity (green) and decreased productivity (red) between 2000 and 2009. (NASA, 2009). Researchers found a global net decrease due to regional drought.


Extreme climate events, including floods and droughts can impact plant functioning, biodiversity and ecosystem processes. However, wetlands have been shown that they can mediate climate change impacts through their multiple ecosystem services. Wet grasslands are adapted to regular disturbance regimes characterised by inundation, cutting and/or grazing. (Brotherton, 2014).


Deserts



One of the most hostile regions on the Earth, deserts can be found near the Tropics of Cancer and Capricorn. Conditions here and often very hot and very dry. The plants and animals that live here have adapted to survive in such harsh conditions and the soils are very thin and sandy.

Although they have low productivity, dryland systems significantly influence Earth’s climate by comprising 41% of the terrestrial land area, 27% of global soil organic carbon, and 95% of soil inorganic carbon reserves (Safriel and Adeel 2005). Approximately 10–20% of the world’s drylands are significantly degraded because of anthropogenic disturbances (Safriel and Adeel 2005). The problem with this is that after severe disturbances, desert soils require long periods of time to recover naturally.

It has been suggested that re-establishing biocrust (biological soils crusts – the living skin of the Earth!) in disturbed drylands may assist with landscape restoration goals because of the significant ecological roles of biocrust organisms. A study carried out in 2016 demonstrated that biocrust inoculation accelerated surface soil recovery and may potentially reverse damage while accelerating restoration of soil stability and nutrient cycling. (Chiquoine et al, 2016).


Polar



The polar regions are located at the north and south poles and support a very specialised community of plants and animals that have adapted to the very cold conditions. One of the most documented victims of climate change, we often hear about the Arctic ice caps melting, sea level rises and threats to polar bears and wildlife.


The polar bear has become the face of Arctic climate change with this image of a starving polar bear being posted to Facebook in 2017, quickly going viral.



Unfortunately, what happens in the Arctic doesn’t stay in the Arctic! The region is warming faster than any other place on Earth, and the world is already feeling the effects. Melting ice caps leading to a rise in sea level threatens coastal towns and cities worldwide. Shrinking sea ice, increased ocean temperature and it’s all stuck in a positive feedback loop. As the Arctic loses snow and ice the high albedo (reflectivity) is reduced exposing bare rock and water that absorb more of the Sun’s energy making it even warmer. This is called the albedo effect.

It has been suggested that if greenhouse gas concentrations continue to increase over the next century, near-surface air temperatures are expected to rise more in the polar regions than in any other part of the Earth (Turner, 2011). This will have serious implications for the cryosphere, oceanic and atmospheric circulations, the marine and terrestrial environments and the indigenous peoples of the Arctic. Arctic sea ice reaches its minimum each September. September Arctic sea ice is now declining at a rate of 12.85 percent per decade, relative to the 1981 to 2010 average. (NASA, 2020). The Antarctic ice sheet mass is also decreasing year on year.


The average monthly Arctic sea ice extent each September since 1979 (NASA, 2020) with 2012 being the lowest recorded.







Antarctic ice sheet mass variation since 2002. (NASA, 2020).









A 2014 study in the journal Nature Geoscience noted, however, that even though 2012 witnessed the lowest summer sea ice extent recorded, the amount of ice recovered substantially in 2013 and 2014. These unexpected freezes were a sign, the authors said, that the Arctic may be able to recover if the world acts quickly to curb climate change. (Tiling, 2015).

Aquatic Ecosystems


Aquatic ecosystems are home to abundance of life including many species of fish, plants and micro-organisms. However, they can also be fragile environments that are directly affected by climate change and pollution. Aquatic Ecosystems are classified into two types, freshwater and marine. Marine ecosystems include coral reefs, mangroves, salt marshes, coastal wetlands and also unique habitats such as estuaries which are brackish water environments with changing salinity. Offshore marine systems include the ocean surface, the deep sea, pelagic oceans or the seafloor. Freshwater ecosystems are terrestrial bodies of water such as freshwater lakes, ponds, streams and rivers.



The biotic components of aquatic ecosystems include organisms and their species, predators, parasites, and competitors. On the contrary, the concentration of nutrients, the temperature, sunlight, turbulence, salinity and density are its abiotic components.




Due to climate change, the temperature of the sea is gradually rising, and this is seriously impacting the species that are able to survive there. For example, coral bleaching is a direct consequence of rising sea temperature. Tiny algae called zooxanthellae live within the corals of the continental shelf. A symbiotic relationship where both organisms benefit from the other. The algae provide nutrients for the coral and the coral in turn provides shelter for the algae. When water is too warm, corals will expel the algae living in their tissues causing the coral to turn completely white. This is called coral bleaching. A study has suggested that corals and calcified algae are potentially more affected by acidification and high solar UV irradiance than non-calcified species. (Williamson, 2019). It stated that the potential for using seaweed aquaculture as a carbon sink and as a strategy for ameliorating increases in anthropogenic emissions of CO2 has been proposed. An interesting idea!

Freshwater ecosystems such as lakes can take the brunt of pollution and human disturbances. For example, farm run off contains nutrients present in fertilisers. An excess of these nutrients in water can lead to eutrophication and hypoxic conditions. In turn this leads to fish mortality due to a decrease in oxygen levels in the water.




A conceptual diagram of (1) the direct effects of ozone depletion and (2) interactions with climate change, on (3) the amount of UV radiation that reaches the surface of aquatic ecosystems. Also shown are (4–9) the factors regulating underwater UV exposure and interactions with climate change, and (10) their consequent effects on aquatic ecosystem services. (Williamson, 2019).

The above only just covers some of the threats facing our many global ecosystems but we can see that climate change is one of the biggest. Here the UK alone we host a wide variety of wetlands, meadows, woodlands and aquatic ecosystems that all need to be protected from the ongoing effects of climate change to the impacts that humans are having on the environment. It might look like a very different world in years to come if we don’t act now…


Thank you for reading


The Climate Corner


References

Brotherton, Sarah J and Joyce, Chris B (2015) ‘Extreme climate events and wet grasslands: plant traits for ecological resilience’, Hydrobiologia. Cham: Springer International Publishing, 750(1), pp. 229–243. doi: 10.1007/s10750-014-2129-5.


Chiquoine LP, Scott AR, Bowker MA (2016). Rapidly restoring biological soil crusts and ecosystem functions in a severely disturbed desert ecosystem, Ecological Applications, 26(4), pp. 1260-1272 [Online]. Available at https://esajournals-onlinelibrary-wiley-com.libezproxy.open.ac.uk/doi/pdfdirect/10.1002/15-0973 (Accessed 20 June 2020)


IPCC (2018). Global Warming of 1.5 °C [Online]. Available at https://www.ipcc.ch/sr15/ (Accessed 19 June 2020).


NASA (2020). Global Climate Change [Online] Available at https://climate.nasa.gov/vital-signs/arctic-sea-# ice/#:~:text=Arctic%20Sea%20Ice%20Minimum,1979%2C%20derived%20from%20satellite%20observations. (Accessed 20 June 2020)


NASA (2009). Terra Video Gallery. [Online] Available at https://www.nasa.gov/mission_pages/terra/videos/index.html (Accessed 20 June 2020)


Runion GB, Prior SA, Rogers HH, Mitchell RJ, (2010). Effects of elevated atmospheric CO2 on two southern forest diseases. New Forests, 39, pp. 275–85.


Safriel U, Adeel Z (2005). Dryland systems. In: Hassan R, Scholes R, Ash N (eds) Ecosystems and human well-being, current state and trends, vol 1. Island Press, Washington, pp 625–658


Shvidenko A, Barber CV, Persson R, (2005). Forest and woodland systems. In: Hassan R,

Scholes R, Ash N, eds. Ecosystems and Human Well-being: Current State and Trends, Vol 1. Washington, DC, USA: Island Press, pp 587–621


Sturrock RN, Frankel SJ, Brown AV, Hennon PE, Kliejunas JT, Lewis KJ, Worrall JJ, Woods AJ, (2011). Climate Change and forest diseases. Plant Pathology, 60, pp. 133-149 [Online]. Available at https://bsppjournals-onlinelibrary-wiley-com.libezproxy.open.ac.uk/doi/pdfdirect/10.1111/j.1365-3059.2010.02406.x (Accessed 19 June 2020).


Tilling, R., Ridout, A., Shepherd, A. et al. (2015). Increased Arctic sea ice volume after anomalously low melting in 2013. Nature Geosci 8, 643–646 (2015). https://doi.org/10.1038/ngeo2489


Turner, J., & Marshall, G. (2011). Climate Change in the Polar Regions. Cambridge: Cambridge University Press. doi:10.1017/CBO9780511975431 [Online]. Available at https://www-cambridge-org.libezproxy.open.ac.uk/core/books/climate-change-in-the-polar-regions/DFFCDE0A1E27390714A1670AEBC6E444 (Accessed 20 June 2020)


Williamson, Craig E et al. (2019) ‘The interactive effects of stratospheric ozone depletion, UV radiation, and climate change on aquatic ecosystems’, 18(3), pp. 717–746. doi: 10.1039/c8pp90062k.