Biodiversity and Climate Change: How They Are Intrinsically Linked

How Does Biodiversity Impact Climate Change?

It has been widely accepted that climate change has a negative impact on our planet’s biodiversity. Recently, it is being acknowledged that one of our biggest hopes for restoring our world is to increase biodiversity. This idea became hugely popularised in Sir David Attenborough’s latest documentary, Life on Our Planet. As Attenborough explains, our earth’s ecosystems are all perfectly balanced and have been for hundreds of thousands of years. Some scientists predict that from as early as the 1830s human activities have been knocking those ecosystems out of balance by releasing greenhouse gases into the atmosphere and heating the planet, altering the earth’s climate at an unnatural speed. These changes to the climate cause huge losses to the earth’s biodiversity which is exemplified in the second half of this article. In turn, the loss of biodiversity increases global warming and so on. A vicious cycle towards an uninhabitable planet. So how exactly does this loss of biodiversity increase global warming?

Our earth has many natural carbon sinks such as mangroves, the oceans, rainforests, wetlands, peatlands and even the soils. These ecosystems are in a fine balance with many species that inhabit them for shelter and food. The loss of species from these ecosystems decreases their efficiency, thus decreasing the amount of carbon they can absorb. Below are a some examples of how this may happen, but don’t forget that this is just a snapshot of the huge biodiversity loss across multiple ecosystems throughout earth.

The oceans are huge carbon sinks, kept healthy by the biodiverse marine species that inhabit them. For example, whales play a big part in the ocean’s carbon dioxide absorption. 10% of the ocean’s absorption of CO2 is due to the plankton that inhabit it, they also produce more than 50% of the oxygen we breathe. These plankton are then eaten by the whales who collectively shuttle nearly 30,000 tons of carbon into the deep sea each year when they die and sink to the bottom. Moreover, the whales excrete nutrients that help phytoplankton grow and increase nutrient availability as they swim from the depths to the surface of the ocean. This means more plankton which means more carbon dioxide absorbed from the atmosphere but also more food for the whales, continuing a beneficial carbon controlling cycle.

Another example of a delicate ecosystem is mangroves. Mangroves are a tropical tree species which thrive in conditions where other trees can’t. They grow in salty, coastal waters and withstand the endless ebb and flow of the tide. They are important in the fight against climate change for two key reasons. Firstly, they help protect us from consequences such as flooding due to storms by slowing water before it hits the land. Secondly, their carbon storage potential is 3-5x higher than that of tropical upland forests due to the strong carbon storage in the soil. CO2 released by global mangrove loss annually could be as high as the annual emissions of Australia. The mangroves are home to a huge range of species from microbes and fungi to 10-foot sharks. They also act as a nursey habitat for many species of fish. In return, the species keep the mangroves alive. Microbes and fungi among the roots use the decaying material as fuel and in return, they recycle nutrients like nitrogen, phosphorus, sulphur, and iron for the mangroves. Birds, butterflies, bees, moths and bats act as essential pollinators for mangroves. The Sonneratia plant opens its flowers at dusk, perfect for the bats to drink the nectar and spread the pollen. Another species, mud lobsters, excavate underground burrows that extend down two meters deep. The excavated mud includes nutrients from decaying matter from deep underground, and the burrows aerate the soil which, in turn, increases water drainage. Initially toxic the mounds of deep, acidic soil come into contact with the air, eventually losing their acidity and become excellent places for little mangroves to grow.

How Does Climate Change Impact Biodiversity?

The increased levels of carbon dioxide in the atmosphere means the Earth’s average temperature is increasing. It is estimated to have increased by 0.7°C since the beginning of the 20th century and, according to the Intergovernmental Panel on Climate Change, could rise by 1.6 – 4.3°C compared to an 1850 – 1900 baseline by 2100.

Some species will be hugely impacted by the changes in temperature alone. For example, Australia’s green ringtail possum cannot control its body temperature when the ambient temperature rises above 30°C, meaning an extended heatwave in north Queensland could kill off large populations. Another example is the green sea turtle. The sex of the turtle is determined by the temperature of the sand incubating the eggs. Warmer temperatures produce females and lower produce males. If we continue to heat our planet the natural gender ratio will be increasingly disturbed causing concern for the longevity of the species who will be unable to reproduce without males.

The increase in sea temperatures will also affect many marine species, including our oceans’ corals. Iconic reefs such as the Great Barrier Reef in Australia and the Northwestern Hawaiian Islands in the US have recently experienced vast amounts of coral bleaching due to an increased sea temperature. It is estimated that 50% of the world’s coral has died in the last 30 years, predicted to rise to 90% with 1.5°C warming and 99% with 2°C warming. These reefs are hugely important as despite covering less than 0.1% of the ocean floor they host more than a quarter of all marine fish species.

Another consequence of high levels of carbon dioxide is that more dissolves from the atmosphere into the ocean, lowering the pH and making the ocean more acidic. Some parts of the ocean are naturally acidic, such as underwater ‘hot springs’ and in the past ocean acidification has occurred naturally but over much longer periods of time. It is now occurring faster than it has in the last 20 million years. The increased acidity will impact any organism with shells or skeletons made from calcium carbonate including sea urchins, sea snails, clams and oysters.

The increased temperatures will make forests fires in countries like Australia, Indonesia, Portugal and California more frequent, larger and more widespread. The unprecedented wildfires in southwestern Australia at the start of last year were estimated to have killed more than a billion animals with many more injured and short of food and water. Obviously, on top of killing so many species, forest fires cause deforestation which only fuels the fire more, figuratively and literally. You can read the ways in which deforestation causes climate change here.

Warmer temperatures cause moisture to evaporate from the ground making periods of low precipitation drier than they would be otherwise. These droughts are already being seen, particularly in Southern African countries such as Zambia and Zimbabwe, where in 2019 the water levels on the Zambezi River were lower than they have been for decades and the usually thundering Victoria Falls had slowed to a trickle. Many animals in these countries will die out due to droughts. African Elephants are in particular danger as they need 40-80 gallons of fresh water a day just to drink.

Whilst dry areas will experience greater droughts, other areas can expect increased storms and flooding due to warming temperatures. As the air warms its water-holding capacity increases, especially over the oceans. According to the Clausius-Clapeyron equation, the air can generally hold around 7% more moisture for every 1°C of temperature rise. Nearly all models predict that India, Bangladesh and Myanmar will become wetter. We have been seeing the worrying increase in storms in these areas leading to vast flooding for many years now. This combined with rising sea levels will cause huge land loss, meaning habitats for some endangered species such as the tiger will be lost.

Increasing temperatures are melting sea ice and glaciers. Not only does this endanger many species through higher sea levels, many species rely on the sea-ice environment such as polar bears who are classified as vulnerable on the IUCN red list. Melting glaciers will cause sea levels to rise, causing low-lying land to become submerged. A sea level rise of only 50cm could: cause sea turtles to lose their nesting beaches; cause Mediterranean Monk Seals, already endangered, to lose beaches to raise their pups; damage shallow coastal areas used annually by whales and dolphins which need shallow, gentle water in order to rear their calves.

Similarly to the forest fires, melting glaciers leads to a vicious cycle as the planet warms up, the icecaps melt, meaning less spots of bright white ice to reflect heat back into space and keep the earth cool.

Across the world we are already seeing and will see more of species’ having to migrate to areas more suitable to them, for example cooler or more moist environments. This will often not be possible due to geographical or human-made barriers and competition from species already in an area. Thousands of species forced to migrate due to climate change are likely to suffer and potentially die out.

Each of these examples represents just a few of the many species at danger from, increasing temperatures making it impossible for them to survive; loss of habitat meaning they have nowhere to go; and inhospitable habitats made inhospitable by ocean acidification, droughts and flooding. Moreover, all species are involved in a complex food web meaning than the loss of one species will inevitably have knock-on effects throughout ecosystems.

This is only a snippet of the affects that climate change and biodiversity have on each other. The intrinsic link between the two can result in either a viscous cycle or, in a thriving ecosystem, a beneficial upwards spiral. We are currently heading towards a perfect storm of eco-system destruction which will in turn make human life increasingly harder. In order to turn this around we need to nurture these delicate ecosystems, ‘rewilding’ the earth as Attenborough puts it, in order to set into motion a beneficial cycle rather than the current destructive one.

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