Biodiversity...Wherefore Art Thou?

Why Biodiversity? As of far, all my posts have considered how we can mitigate climate change, the obvious benefit lies in the positive environmental impacts for humans of doing so. This post moves away from this rhetoric to analyse the effect climate change has had on the global biodiversity and just how the mitigation proposals that we have had may influence the biodiversity of our fragile earth!

Biodiversity is an important aspect of the earth, and the term encompasses the expansive and complex number of species, organisms and ecosystem variability (Sungupta 2013) across the globe. Biodiversity is an important consideration in the context of climate change – the modifications in environment that climate change brings about results in immense pressures for biodiversity on various levels.

Considering biodiversity is of importance as it provides multiple ecosystem services that sustain earth. One important impact of climate change is that the decline in genetic variation can reduce the ability of a specie or ecosystem to remain resilient against environmental change, potentially destabilising the ecosystem. Consequently, an interruption, due to habitat degradation in a single part of the ecosystem or a single species of plant and animal can have consequential impacts that that can create a domino effect and further effect biodiversity negatively (Sungupta 2013).

Case study: Antarctica

There are many different scenarios in which climate change has threatened biodiversity. Notably the collapse of the Larsen-A/B Ice Shelf in Antarctica, due to rise in global temperatures, was a dramatic change for that area (figure 1).

Figure 1. Larsen-A Ice Shelf pre-collapse extent (1995) and Larsen-B Ice Shelf Pre-Collapse Extent (2002) (Source: Spiegel Online).

Gutt et al’s (2011) paper identifies the multiple impacts to the biodiversity around the Larsen Shelf. The impacts on the benthic community in the area around the Larsen-B embayment show signs of impoverishment. Further, the collapse of the Larsen-B shelf has led to a large amount of ice being deposited in the water – which led to considerable scour at 7% around the embayment. Re-colonisation of benthic species here did not match the comparative Weddell Sea recolonization rates of 4-59%. Although recolonization rates did not match the Weddell Sea reference, it should be recognised that there was not a drastic negative impact for the biodiversity of the area -  in fact there was a strong beta diversity recorded at the Larsen-B study areas despite the scouring.

Case Study: Great Barrier Reef: Australia

The Great Barrier Reef is the planets largest coral reef barrier, located off the coast of Queensland in the Coral Sea. The reef of recent has been in the headlines as it has been announced that it is under tremendous stress and nearly ‘dead’. The reef is an important ecosystem. Hoegh-Guldberg et al (2007) identify that the reef provides irreplaceable ecosystem services to the area of Queensland, namely coastal protection and a source of tourism, not to mention the vast diversity of species that create a unique biodiversity.

But the system is under pressure due to climate change and the continued pumping of anthropogenic carbon dioxide into the atmosphere – the ocean acting as a carbon sink, sequesters this carbon. However, this is ultimately damaging for the coral reef biodiversity in the Great Barrier Reef.

The presence of CO₂ increases the acidity of the ocean water and utilises carbonating ions in the water, reducing the availability of carbonate-ion concentrated water which coral rely on to thrive – ultimately leading to a slowdown in coral calcification as ocean acidification increases. Rising temperatures caused by climate change also contribute to the decimation of the Great Barrier Reef, the warmer temperatures effect corals and their endosymbiotic dinoflagellates (Symbiodinium spp.), Symbiodinium spp. plays an important role in the maintenance of the reef where it sustains coral by entrapping 95% of solar energy and nutrients utilised by the coral. The process of nutrient and solar trapping disintegrates as the rising temperatures negatively affect Symbiodinium spp. leading ultimately to the bleaching of coral as it reduces the ability of coral to maintain calcification (Hoegh-Guldberg et al 2007).

Essentially, the ocean acidification to the Great Barrier Reef and the effect of rising temperatures has delivered a double blow. The Australian Government acknowledges, that ocean acidification action is a significant actor of destroying the biodiversity of the ecosystem.

Predicting the Impact of Climatic Change on Biodiversity:

Climate change is not the only factor involved that can influence biodiversity, the change in land uses creating habitat fragmentation can interrupt important corridors that species use for migration. Together, the influence of climate change and land use change means that species that are migratory are having to travel longer routes to reach their destination – ultimately effecting the biodiversity of an area if species cannot reach where they want to get. McGuire et al (2016) found that species which dwell in ‘65% of natural area could track their current climates, allowing them to adjust to 2.7 °C more temperature change’, meaning that there is the potential of species to adjust to climate change but the interference of land barriers to movement hinders this potential.