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Carbon sinks extract carbon dioxide from the atmosphere and absorb more carbon than they release. Carbon sources, conversely, release more carbon than they absorb. They cover about 30% of the Earth’s land surface and as much as 45% of the carbon stored on land is tied up in these sinks. Carbon sinks are therefore an essential means of helping fight climate change, but without major changes to current human practices, they are unable to mitigate the detrimental effects alone. 

The Carbon Cycle 

The carbon cycle refers to the natural flow of carbon between the ocean, rocks, fossil fuels and living organisms. Forests are examples of carbon sinks as trees and plants extract carbon dioxide from the atmosphere through photosynthesis – some is also stored. When plants die, the carbon dissolves into the soil where microbes are then able to release the carbon back into the atmosphere by process of decomposition, where it’s available to other plants for photosynthesis.

Oceans are considered to be the main natural carbon sinks, absorbing approximately 50% of the carbon emitted into the atmosphere. Plankton, corals, fish, algae and other photosynthetic bacteria contribute to this extraction of carbon

Any process that uses fossil fuels – such as burning coal to generate electricity – releases more carbon into the atmosphere than carbon sinks can absorb. Cattle farming also releases a lot of carbon into the atmosphere. It also contributes to deforestation, depleting the planet of its carbon sinks; according to the World Resources Institute, farms emitted 6.6 billions tons of greenhouse gases in 2011, equivalent to about 13% of total emissions. The agricultural sector is the world’s second largest emitter of GHGs, after the energy sector. 

Ideally, the carbon cycle would maintain Earth’s carbon concentration, helping to move carbon from one location to the next and keeping atmospheric carbon levels stable. However, due to human activity, the carbon cycle is changing: we are releasing more carbon into the atmosphere than Earth can handle by using fossil fuels and maintaining large livestock operations. Deforestation is further exacerbating this problem as it depletes the Earth’s  supply of carbon sinks. Since 2016, an average of 28 million hectares have been cut down every year, equivalent to one football field of forest lost every second. Consequently, the amount of carbon in the atmosphere is rising. 

Solutions to combat this problem include banning deforestation, planting more trees, utilising renewable energy sources and reducing the use of fossil fuels.

Carbons Sinks Examples

Aside from the aforementioned oceans being the main natural carbon sink in the world, forests are also significant carbon sinks examples as well. According to a report published in January 2021, forests absorb twice as much carbon as they release each year,  absorbing a net 7.6 billion metric tonnes of carbon dioxide annually.

As the world’s largest and best known tropical rainforest, the Amazon accounts for just over a third of tree cover across the tropics and is one of the most important natural carbon sinks in the world.  Their role is more important than ever especially as the world’s carbon emissions exponentially increase over the last few decades. However, recent studies have recorded the Amazon releasing higher carbon emissions than absorbing it due to deforestation and higher rates of wildfires.

Similarly, mangroves are highly regarded in their role of absorbing and capturing carbon in the atmosphere, and in fact, have been known to be a more effective carbon sink than forests. Mangroves have been recorded to absorb almost 10 times as much carbon dioxide from the atmosphere than terrestrial forests. Indonesia currently boasts the world’s largest mangrove ecosystem, accounting 23% of the world’s total.

Recent research in what has been dubbed as the world’s largest seagrass project, has also found seagrass to be a particularly effective carbon sink and hugely successful in restoring oceans and  purifying the water.

You might also like: What is the Kyoto Protocol?

carbon sinks

(Source: Earth.Org) 

Artificial Techniques 

In addition to natural carbon sinks, technological advances have helped produce artificial techniques that extract carbon from the atmosphere. 

Examples include: using geological carbon sequestration techniques that inject carbon dioxide into deep saline aquifers to produce large pockets of salt water; injecting carbon dioxide emissions from coal-fired power stations deep under the Earth’s surface and using light-sensitive algae that are capable of absorbing carbon dioxide and emitting oxygen.

Artificial technologies, however, are not efficient or advanced enough to cope with the effects of the climate crisis. Investing in research and companies who commit to finding alternate ways of extracting carbon dioxide from the atmosphere will prove worthwhile.

Since the Industrial Revolution, fossil fuel technologies have been driving economic growth, so reducing emissions may appear to threaten developing countries’ progress, but to meet the Paris target, this is exactly what needs to happen. Is there a way for developing countries to prosper without increasing their emissions? 

How Do Developing Countries Contribute to Climate Change?

A study from the World Resources Institute in 2017 reveals that the world’s top three emitters of greenhouse gases, namely China, the European Union and the US, contribute more than half of the total global emissions while six of the top 10 emitters are developing countries. 

The World Economic Forum recognises that carbon emissions and developing countries being lifted out of extreme poverty are linked. An increase in carbon emissions observed over 30 years shows that poverty has been reduced within East Asia and Pacific and South Asia, while sub-Saharan Africa has, during the same time period, reduced their emissions and almost doubled the number of people living in poverty.

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Moreover, The Paris Agreement acknowledges that the efforts toward reducing carbon emissions will be common but not equal among developed and developing countries. The fairness of these contributions will be determined by national circumstances so that there will be equity in the responses and responsibilities to address climate change. This means that developing countries will be allowed to emit more carbon until they have developed enough that they no longer need to rely on carbon-intensive industries. 

However, data compiled by the World Resources Institute shows that since 2000, 21 developing countries have reduced annual emissions while simultaneously growing their economies, indicating that the decoupling of economic growth with emissions is possible.

Similarly, The Low Carbon Index found that several G20 countries have reduced their economies’ carbon intensity while maintaining GDP growth, including countries classified as ‘developing’, such as China, India, South Africa and Mexico. 

While global carbon emissions have nevertheless been rising exponentially over the past decade, the International Energy Agency reported three years of flat emissions globally, from 2014 to 2016, as the global economy grew. A study conducted in 2017 investigated whether renewable energy has anything to do with this decoupling. The findings indicated that the nations that generated more electricity from renewable resources had lower carbon emissions overall, illustrating that renewable energy is able to support economic growth while reducing emissions. 

Clean Economic Growth for Sustainable Development

According to the Renewable Energy Policy Network for the 21st Century’s (REN21) yearly overview of the global state of renewable energy, it made up 24.5% of global electricity generation in 2016. This went up to 26.5% in 2017, but by the end of 2018, it had gone down to 26.2%. While the adoption of renewable energy is steadily increasing, it is not enough to have a significant impact in the long term and needs to be adopted on a much larger scale. 

According to an International Energy Agency report, Africa has the richest solar resources but has installed only 5 GW of solar photovoltaics (PV), less than 1% of global capacity. Aiming to provide electricity for everyone on the continent would require a significant increase in electricity generation, with only 43% of Africans currently having a reliable power supply. According to the report, electricity demand on the continent will more than double by 2040.

The report indicates that with the right policies, Africa can meet the demand by relying on renewable energy, with solar energy having the potential to be its top renewable energy source, exceeding hydropower. That renewable energy is now the cheapest source of energy generation makes this all the more possible. “A focus on energy efficiency can support economic growth while curbing the increase in energy demand,” the report says. 

Africa’s endeavour to meet its energy needs in a renewable way while providing its inhabitants with a good quality of life should serve as inspiration for other developing nations.

There is evidently a huge opportunity for developing countries to generate energy sustainably. Renewable energy sources deliver economic benefits without the risks of fossil fuels; such benefits include creating more job opportunities in the energy sector and achieving energy independence.

Developing Countries Cannot Afford Renewable Energy

However, there are significant barriers that prevent developing countries from adopting renewable energy plans. Decarbonisation is often not a priority for less developed countries compared to economic growth and poverty alleviation. Many of these countries struggle with gaps in technical and financial expertise, a lack of resources and poor governance. 

Creating lowest-emission or renewable energy strategies shaped to each country’s unique circumstances is vital to maintaining and encouraging growth while reducing emissions. 

Developing countries need to implement policies that shift the economy away from carbon-intensive industries. These should be coordinated at a global level to ensure a worldwide shift towards an equitable and environmentally responsible future. 

Historically, our planet’s land and oceans have functioned as major ‘sinks’ in the global carbon cycle, together absorbing about half of global carbon emissions. Unfortunately, their carbon sequestering effectiveness is rapidly diminishing as temperatures rise, to the extent that carbon deposits on land may become net greenhouse gas emitters by mid-century if climate policies remain unchanged. How can this phenomenon be explained, and how are its risks mitigated?

Over the past 150 years, human activities have emitted about 545GtC (Gigatonnes) of carbon, with fossil fuel combustion comprising approximately three-quarters of this. Since terrestrial and marine biomes have each absorbed at least 30% of these emissions, effects of global warming have been significantly restrained. However, their capacity for carbon storage is fundamentally dependent on environmental determinants and can hence be severely reduced in hotter or drier climates.

The Importance of Carbon Cycle

Most carbon on land is locked up in tropical rainforests, peatlands and permafrost. While higher CO2 concentrations initially stimulate vegetation growth by facilitating photosynthesis, these benefits are rapidly overshadowed by falling soil moisture amid rising temperatures, causing plants to dehydrate and die. Not only is carbon fixation directly reduced from plummeting productivity or death of plants, lower transpiration rates mean that rainfall is diminished, giving rise to hotter and drier climates. This creates ideal settings for fires to ignite or spread, releasing more CO2 into the atmosphere in a positive feedback loop. In 2019 alone, fires in Indonesia’s dry forests and peatlands emitted  more than 708 million tons of greenhouse gases, dwarfing the 366 million tons emitted from the Brazilian Amazon fires.

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global carbon cycle
Global carbon cycle diagram explaining the fast carbon cycle (Source: U.S. DOE, Biological and Environmental Research Information System at https://earthobservatory.nasa.gov/features/CarbonCycle )

Outside the tropics, rising temperatures cause permafrost soils in polar regions to thaw. Notably, permafrost thaw in Russia allows decomposition of its largely-preserved organic material into carbon dioxide and methane, raising atmospheric carbon concentrations while undermining the stability of existing infrastructure. In oceans, warmer water temperatures reduce the solubility of carbon dioxide gases and impede its flow to greater depths, a process called ‘vertical mixing’, and may deprive phytoplankton of the nutrients they need to drive the biological carbon pump. More dangerous, however, would be the melting of deep-ocean methane hydrate, where methane is frozen in ice deposits. Despite potential applications as an alternative energy source, its release of trapped methane has been theorised to be a primary contributor in the end-Permian mass extinction. Though such occurrences are unlikely without significant spikes in water temperature, such potentially devastating consequences cannot be disregarded, especially when mean ocean temperature is already projected to rise by up to 4°C by 2100.

To disrupt these positive feedback loops in the global carbon-cycle, extensive reforestation or carbon capture and sequestration (CCS) are commonly proposed as mitigation strategies to offset our carbon footprint, however neither route can function as a silver-bullet for anthropogenic climate change by itself, unless the root causes of human-induced carbon emissions are fundamentally addressed. Doing so necessitates substantial coordination of climate policies in all major economies to disincentivise greenhouse gas emissions, notably through carbon-pricing mechanisms such as ‘cap-and-trade’ or Pigouvian taxation. Whilst transition risks may pose significant short-term disruptions, substantial action is necessary to prevent uncontrolled global warming in the long-term. 

While commercial whaling is banned, it is estimated that at least 1 500 large whales are killed each year. While the problem of dwindling whale numbers is oft-discussed, what is less known about whales is the role they play in mitigating global warming. 

Whales are hunted for their blubber, meat and bones. The blubber is used in whale oil, which was widely used in cars as an automatic transmission fluid as well as a lubricant. However, whales are worth much more as a biofuel and they play a vital role in the global ecosystem to mitigate global warming.

 The International Monetary Fund (IMF) has estimated the value of a single great whale at more than US$2 million, amounting to more than US$1 trillion for the current stock of great whales. This amount was determined based on each whale’s contribution to carbon capture, the fishing industry and the whale-watching sector. 

Whales and the Carbon Cycle

Whales are capable of capturing a significant amount of carbon from the atmosphere. A great whale’s diet consists largely of phytoplankton, a microscopic plant that converts sunlight and carbon dioxide into carbohydrates and by extension, oxygen. A single whale can- over a lifespan of around 60 years-  accumulate around 33 tonnes of CO2 on average. By comparison, a tree can absorb up to 22kgs of CO2 a year. 

When whales defecate, the nutrients (iron and nitrogen) released from their fecal plumes stimulate phytoplankton growth which attracts fish and other organisms, a phenomenon known as ‘whale pump’. 

Phytoplankton contribute at least 50% of the oxygen in the Earth’s atmosphere and capture an estimated 37 billion tonnes of all CO2 produced. This is equivalent to the amount of CO2 captured by 1.7 trillion trees, four times the number of trees in the Amazon Rainforest. The IMF study also stated that a 1% increase in phytoplankton productivity linked to whale activity could mean the capture of the equivalent of planting 2 billion mature trees. 

Even the (natural) death of a whale serves a crucial function. Whale carcasses sink to the seafloor, and the carbon stored in the carcasses is able to support deep-sea ecosystems and become marine sediments, with carbon being locked away for hundreds of years.

The carbon cycle of whale-phytoplankton positive feedback (Source: International Monetary Fund).

Whaling and the Environment

Whaling has been a tradition in many cultures since 3000 BC. Since industrialisation in the 1860s, the intensity of whaling reached its peak in the 1960s, with a maximum of more than 90 000 whales caught a year during this decade. Many species of whales became critically endangered during this time, such as the humpback and right whale.

Solutions to Whaling

In 1982, the United Nations Conference on the Human Environment and International Whaling Commission (IWC) passed a vote to ban commercial whaling. All commercial whaling activities are banned but member nations can issue ‘scientific permits’ for whaling. There is an ongoing issue of Japan abusing the system by using lethal methods to conduct what they call research on whales, whose meat is still widely available on the market in Japan. 

In 2018, IWC members discussed and rejected a proposal by Japan to renew commercial whaling. Through the Florianopolis Declaration, it was concluded that the purpose of the IWC is the conservation of whales and that they would safeguard the marine mammals in perpetuity to allow for the recovery of all whale populations to pre-industrial whaling levels. In response to this, Japan announced that it believed that the IWC had failed in its duty to promote sustainable hunting. It withdrew its membership from the IWC and resumed commercial hunting in its territorial waters in July 2019, but claimed that it would cease whaling activities in the Southern Hemisphere. 

The whaling industry in Japan has this year received a subsidy of US $47 million from the government to continue whaling. This controversial decision has been criticised by environmental and conservation NGOs such as the Sea Shepherd, Greenpeace and WWF. 

Besides whaling, other threats facing whale populations include overfishing, collisions with  ships and interference with their communication systems caused by noise from large ships.  

If whales were to return to their pre-whaling numbers of 4- to 5 million (up from 1.3 million today), researchers say they could capture 1.7 billion tonnes of CO2 annually. 

Meanwhile, the concentration of carbon dioxide in the atmosphere is increasing rapidly. The levels of CO2 is currently at just over 411 parts per million

A recognition of the contribution that whales make in the fight against global warming and climate change could be a valuable alternative to high-tech solutions or expensive programmes. Humanity needs to change its attitudes to recognise that all organisms serve an important role in the global ecosystem.  

Featured image by: Dr Louis M. Herman

As the world’s climate changes, the rate of ocean warming is accelerating at an unprecedented rate, sea levels are rising and many ocean species are dying out. However, one species not feeling the heat, but is in fact thriving in warm waters spurred on by the climate crisis, is the jellyfish. 

Global climate change has been causing a sustained warming of the oceans since 1970. It has likely been happening at an increasingly rapid rate since 1993, and with no reduction in intensity, according to the most recent report by the Intergovernmental Panel for Climate Change (IPCC). Despite this, the jellyfish is thriving in the fertiliser-rich, deoxygenated warm ocean waters. 

Jellyfish Facts

Putting a number on jellyfish populations is difficult due to a lack of quantitative records. However, a study showed that jellyfish populations have increased in at least 68 ecosystems around the world since 1950 and ‘are one of the few groups of organisms that may benefit from the continued anthropogenic impacts on the world’s biosphere’. 

Jellyfish Bloom

Jellyfish populations fluctuate in blooming cycles naturally. However, the recent growth  is correlated with man-made changes to the environment. Blooms of the giant jellyfish (Nemopilema nomurai), which have historically happened in Japan once every 40 or so years, have become a yearly occurrence since the early 2000s. The animals cause many problems, such as clogging fishing nets, affecting tourism in places that rely heavily on its oceans, stinging people, killing fish by lodging within gills and clogging cooling screens in power plants, amongst others. In June 2018, over 1000 people were stung by jellyfish in a single week in Florida. 

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Jellyfish are also particularly dangerous near nuclear coastal power plants. To prevent a disaster whereby a swarm of jellies block an underwater cooling system, costly shut-downs, such as in Torness (UK, 2011), or Oskarshamn (Sweden, 2013) are necessary. 

The gelatinous animals owe their explosion in numbers to a variety of factors, as outlined in a report by the Union of Concerned Scientists and below.

The warm waters are forcing tropical coral reefs to seek more temperate regions, a migration that has been happening at a rate of 8.7 miles per year since the 1930s. Migrating coral makes way for other marine species- including jellyfish- to extend their habitable territory. This throws the local ecosystems off-balance as jellyfish join the competition for zooplankton, as well as hinder the lives of fish by eating their eggs, larvae and juveniles, according to the Earth Institute of the University of Colombia. Increases in populations of nonindigenous species are possibly the most damaging of all.  

Additionally, oceans are dumping grounds for carbon, which further aid jellyfish. IPCC models show that as the concentration of atmospheric CO2 since the beginning of the century has increased, so has the oceanic absorption that has led to warm waters for jellyfish. It is estimated that within this time frame, oceans have absorbed 20-30% of total man-made emissions globally.

The rise of CO2 in the atmosphere means that more CO2 gets absorbed into seawater. This carbon reacts with water molecules to form carbonic acid, which then breaks down into hydrogen and bicarbonate. The presence of all these hydrogen ions this reaction creates causes the water to become more acidic. Gases dissolve more readily in cooler waters and so acidification is more pronounced in the Arctic and Southern oceans. This acidity inhibits coral growth and causes reefs to die off in a process called ‘coral bleaching,’ allowing jellyfish to roam and multiply freely.

Anthropogenic influences significantly impact jellyfish populations. Fertiliser and effluent sewage from land cause oversaturation of water with nutrients, particularly around coastal estuaries – a process known as eutrophication – enabling excessive algal growth. Decaying algae depletes water of oxygen. Jellyfish are able to tolerate low concentrations of oxygen and with plentiful food, they continue to multiply, while other fish suffocate and die. Additionally, coastal development, the building of docks, boats anchored in harbours and underwater infrastructure provide perfect surfaces for breeding jellyfish to attach to in their polyp stage.

Finally, the overfishing of species which prey on jellyfish, such as tuna and sea turtles, means that jellyfish are able to breed undeterred by predators. According to Dr Callum Roberts, a marine biologist and author of the seminal book “The Ocean of Life,” humans take 50% more fish than thought – “a staggering total of about 130 million tonnes a year.” He explains that the issue of fishery mismanagement and the release of misleading statistics can lead us to circumstances ‘beyond our capacity to cope.’ 

Another aspect spurring on the jellyfish’s population growth is the fact that at least five known species are effectively immortal. 

The phenomenon was first observed in Turritopsis dohrnii, the ‘immortal jellyfish.’ Not unlike the mythical phoenix, from the dead body of a jellyfish springs a new one into life. 

Dr Lisa-ann Gershwin, director of the Marine Stinger Advisory Service in Tasmania and jellyfish researcher, explains on a BBC Earth podcast episode

“When Turritopsis dies its body begins to decay, as it would, but then the cells reaggregate into polyps – it skips to the alternate part of its life cycle, the earlier life stage. These little polyps keep cloning and they can cover an entire dock in a matter of few days! Some types can form whole ‘shrubs’ and when the conditions are right they bloom in vast numbers like flowers and ‘bud off’ baby jellyfish.”

The more common moon jelly has also been shown to defy death. Observing the same ability in both is a surprising, complex and hopeful discovery. 

With the rapid expansion of these populations, scientists and policymakers are brainstorming ways of making the animals useful. The GoJelly project proposes employing the creatures’ ability to use their mucus to bind microplastic. The researchers intend to develop a microplastics filter to be used in wastewater treatment plans and in factories where microplastic is produced, which could help prevent much of these particles from getting into marine ecosystems and harming wildlife further.  

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