The amount of carbon dioxide in the atmosphere has now passed 400 parts per million (ppm), meaning that humans will have to face up to climate consequences over the next few decades. With COP 22 taking place this month, World Land Trust (WLT) investigates the relationship between tropical ecosystems and climate change, and how the Trust is reducing emissions through conservation.
What does 400 ppm mean?
400 parts per million of carbon dioxide is widely considered the point when the emissions in the Earth’s atmosphere reach a level that is irreversible in our lifetime.
The level of carbon dioxide in the atmosphere varies over the year, with September usually marking the year’s lowest carbon dioxide levels. As the Northern hemisphere transitions in to autumn, the effects of plants growing and sucking up carbon dioxide from the atmosphere during the summer fades, before leaves are lost and decompose, releasing some of the stored carbon back into the atmosphere.
Although the atmosphere surpassed the 400 ppm level in the Northern Hemisphere back in May 2012, this figure remaining in September means that this threshold has been crossed for good, unlikely to return below it in our lifetimes. Even if carbon emissions were to be completely eradicated, it would take decades to remove the emissions humans have pumped into the atmosphere since the Industrial Revolution.
Impacts of climate change
At last year’s UN Climate Change Conference in Paris (COP 21), 195 countries committed to a global action plan to keep warming below the global average temperature of 1.5 degrees Celsius above pre-industrial levels, citing 450 ppm as the limit. However, in an article published in Scientific American Online, climate scientist Dr Michael Mann states that to avoid two degrees of warming, carbon dioxide levels should be held to 405 ppm.
There are many serious impacts of a global temperature increase, including: a rise in global sea level; threats to food security; human health implications and a greater frequency of extreme climate events such as wildfires, droughts and hurricanes.
What role do ecosystems play?
Tropical ecosystems, including forests, act as one of our primary defences against climate change. Forests are inextricably linked to Earth’s climate, by taking in more carbon dioxide than they release trees act as ‘carbon sinks’, extracting carbon dioxide out of the atmosphere and locking it away.
However, despite their role in combatting carbon emissions, these ecosystems face a constant struggle against climate change, particularly rising temperatures. Historic changes in temperature have usually happened at such a low rate (over centuries) that plants have been able to evolve to adapt to cope with the changes. Even then, the plant species incapable of adapting fast enough are wiped out of the ecosystem by their competitors, beaten by natural selection. However, the current temperature is rising so rapidly that evolution cannot keep up, which will cause extinctions of animal and plant species across the world.
Vicious cycles: forests, oceans and reefs
It has also been calculated that in a warmer climate, tropical ecosystems will not be able to hold as much carbon as they do currently, creating a vicious cycle of increasing carbon dioxide. This does not just apply to forests. The world’s oceans are also carbon sinks providing a buffer to climate change; a warmer ocean cannot hold as much dissolved carbon dioxide.
Coral reef ecosystems also hold significant carbon sinks in the form of bioherms, the calcified remains of coral which form over hundreds of years, storing carbon withdrawn from the ocean. Even though bioherm carbon storage is not yet well understood, the mass bleaching event of the Great Barrier Reef (caused by anthropogenic warming) could also have consequences for carbon dioxide levels.
What can be done?
For the targets set by the Paris agreement to be met, emissions would need to be reduced to ‘net zero’ in the second half of this century, including through avoiding land use change that results in carbon emissions (such as deforestation), as well as a clean energy revolution.
Through conserving habitats we have a twofold effect – firstly creating offsets and secondly by protecting vulnerable ecosystems. Preserving biodiversity is essential for ecosystems to adapt to climate change. Healthy and resilient ecosystems have a greater potential to mitigate climate change, being able to resist and recover from its effects more easily.
‘Offsetting’ or ‘balancing’ emissions is one of the three steps of World Land Trust’s Carbon Balanced Programme. This initiative works by offsetting unavoidable emissions by protecting valuable carbon sinks in the form of biodiverse tropical ecosystems under imminent threat of deforestation or degradation. It is estimated that the deforestation and land use change of tropical ecosystems accounts for 10 to 20 per cent of anthropogenic emissions globally.
Carbon Balancing is an ongoing process underpinned by three key steps. The first step is to measure carbon emissions, followed by an assessment of which emissions can be reduced. This is a vital part of the process, and speaks to the commitment of carbon balancing- it is not enough to offset emissions without reducing wherever possible. Only once emissions have been measured and reduced can they be offset.
Ecosystems play a pivotal role in the fight against climate change and their protection is imperative, not only for the species that live within them, but to help mitigate the threat they are facing.