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New laser technology has been developed to allow scientists to look into the internal structures of giant larvaceans, deep-sea marine animals that are vital in ocean ecosystems. These animals have mucus, or “snot houses,” that inadvertently contribute to the ocean carbon cycle and microplastic transport in the deep sea environment. How does this small creature play a role in filtering tiny plastic particles and assisting in carbon sequestration? 

Giant larvaceans are planktonic marine invertebrates in the open ocean. They can be as large as 10 centimeters in size, while the house can extend itself to 1 meter. 

It has been discovered that many gelatinous animals build balloon-like mucous structures called “houses,” which concentrate food by filtering tiny particles out of the surrounding seawater, as much as 21 gallons of water per hour. These particles contain organic carbon, some of which come from the atmosphere as carbon dioxide. These structures eventually become overloaded with particles- usually every 24 hours- and the larvacean abandons its house. This house then sinks to the seafloor, where it is consumed by animals or buried. The buried carbon is unlikely to return to the atmosphere for millions of years. In this way, they play a significant role in moving carbon from the upper part of the ocean into the deep sea. 

It has previously been challenging to make in-situ long-term observations of these species in the midwater ocean since they are too fragile to capture with plankton nets. Scientists have adopted new laser technology to reconstruct 3-D images of the interior structure of the giant larvacean, which show the mucous house morphology, and how they feed themselves by regulating the incoming water flow and concentrating particles using their “houses.” 

How long this mucous filter lasts depends on the size of the larvacean, but giant larvaceans typically build a new house daily. The filtration of the house is highly efficient. During the spring months, when they are most abundant, larvaceans surveyed in Monterey Bay were able to filter the water between 100 and 300 meters in the Bay in as little as 13 days, the equivalent of 500 Olympic-sized swimming pools per hour.

This creature has also been found to filter microplastics in water. 

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Carbon Capture by Larvaceans 

Giant larvaceans are an important part of the biological pump in the ocean, or the ocean carbon cycle. Their houses contain carbon and when they abandon them, they are transported from the near-surface waters to the deep sea benthos, bringing the carbon down with it. This process is responsible for as much as one-third of the carbon flux from surface waters to the deep ocean. 

Microplastic Capture 

Given that microplastics have become very prevalent in the ocean, some marine organisms may serve as a biological vector that incorporates microplastic into the food web. Scientists observed that giant larvaceans also ingest microplastic particles, but they are capable of rejecting microplastics due to the low nutritious value. When they abandon their mucous filters, they travel quickly to the seafloor, at a rate of about 800 meters a day. 

Ecological Function of the Snot House

The house also serves a vital function to the larvaceans. The house contains two layers; the outer shell, which is coarse-meshed, and the inner house, which is in a finer mesh. The outer shell protects the inner house from clogging or getting damaged by large particles. 

The house also helps to protect the larvacean against predators by helping them to avoid direct contact with predators e.g. jellyfish. It also helps the larvacean to camouflage itself from mechanosensing predators by reducing the flow generated by the beating tails.

The larvacean’s ability to sequester carbon and lock it away is another example of a vital ecosystem service that inhabitants of the oceans perform in maintaining the ocean carbon cycle. Warming oceans as a result of the climate crisis will affect these- and other- creatures’ ability to continue to perform these services. These creatures can also teach scientists new ways to design filters or expandable structures that perform similar jobs as larvaceans. 

Featured image by: MBARI

Anthropogenic climate change is having a profound effect on forest dynamics worldwide, a new study finds. Rising temperatures and increasing CO2 emissions, in combination with extreme weather events and deforestation that are all accelerating the climate crisis, are driving the shift towards younger and shorter trees in forested ecosystems, presenting worrying consequences for both the carbon storage capacity and biodiversity of the world’s forests.

In order to evaluate how the climate crisis and other disturbances affect tree populations worldwide, researchers focused on determining the response of forests to longer term climatic changes, as well as short-lived disturbances, and combined these findings with global land-use change and disturbance data-sets. 

Nate McDowell, who led the study at the US Department of Energy’s Pacific Northwest National Laboratory, describes how “Over the last hundred years we have lost a lot of old forests” and emphasises that “They’ve been replaced in part by non-forests and in part by young forests. This has consequences on biodiversity, climate mitigation, and forestry.”

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Forest dynamics are governed by three primary processes, namely recruitment – the rate at which seedlings are added to a population, growth – the rate of biomass production, and mortality – the loss of a plant’s reproductive ability. Other natural disturbances such as wildfires and droughts, as well as land-use changes, interact with these processes, which ultimately alters biomass and species composition.

Europe and much of the Americas are already witnessing these shifts towards younger and shorter forests, where analysis reveals that over the past 40 years, tree mortality rates have doubled. Tom Pugh, a scientist from the University of Birmingham who was involved with the analysis, highlights how unnaturally young and short forests occupy much of the UK and Europe, he says “They are not of the stature that many of those forests would have been before humans fundamentally changed them by harvesting at regular intervals and planting new species.”

The study found that the percentage of trees younger than 140 years old has increased from 11% of forested area in 1900 to 34% in 2015, as a direct result of land use changes and wood harvesting. Due to limited data, researchers were unable to confidently estimate how much shorter trees have become.

Impact of Climate Change on Forests

Increases in temperature is one driver of tree mortality as it causes the stomata of plants to close whilst limiting the process of photosynthesis, vital for plant growth. This not only causes greater levels of tree mortality but also hinders regeneration. This causes larger plants to die, with those replacing them being smaller in size. 

The effect of CO2 on forest dynamics is slightly more complex. Higher levels of CO2 in the atmosphere can actually trigger growth in young forests, as long as there is an abundance of nutrients. Where forests have insufficient access to nutrients and water, the benefit of increased CO2 emissions isn’t as pronounced. Some of the studies analysed suggest that increases in atmospheric COmay actually increase tree mortality rates.

As well as these longer term changes in climate and CO2 concentrations, forests are constantly being threatened by a number of extreme weather events, made more frequent and severe due to anthropogenic climate change, as well as deforestation. Whilst the different disturbances have varying impacts on forest dynamics, the overall trend is that tree mortality is consistently increasing, causing plants to be both shorter and younger.

Whilst recruitment and growth rates are expected to vary over time as well as geographically, the evidence suggests tree mortality rates will continue to increase in the future resulting in reduced forest canopy cover and biomass. There is however some uncertainty surrounding several feedback mechanisms, triggered by climate change and other disturbances, which could help to mitigate these changes to forest dynamics. These mechanisms include the ability of forests to adjust to changes in climate, adapt to a range of biotic (living) and abiotic (non-living) factors and to migrate in response to changing climatic and environmental conditions.

Why are forests important for mitigating climate change?

Forests act as a vital carbon sink for greenhouse gas emissions, however shifting forest dynamics pose serious implications for the total terrestrial carbon storage available. Increased plant mortality, along with limited recruitment or growth, significantly reduces the carbon storage potential since younger forests aren’t able to store as much carbon as older forests. This raises additional challenges to the global effort of tackling the climate crisis. 

In a study published in March, scientists made the concerning discovery that intact tropical forests absorbed 46 billion tonnes of carbon in the 1990s but by 2010, this had decreased by a third to 25 billion tonnes. Critically, forests absorbed 17% of human induced carbon dioxide emissions in the 1990s, compared to just 6% in 2010, highlighting the worrying trend of reduced carbon storage capacity of the world’s forests, where they could move from being sinks of carbon to sources of carbon. 

Professor Simon Lewis at University College London sheds some more optimistic light on this research as he explains: “Because old-growth forest is being lost, then on average, across the globe, forests are getting shorter and younger. Yet, counter to this, and what the researchers don’t highlight is that within many old-growth forests the opposite is happening.” He argues that: “The world’s intact tropical and boreal forests are both globally important as carbon sinks, and are getting larger.” 

He also raises the crucial point that ‘the world’s forests currently slow the climate crisis, and while future mortality trends could reverse this, the ideas in the new report don’t change what the world needs to do: stabilise the climate by quickly driving fossil fuel emissions to zero and protect the world’s forests’.

This study raises greater awareness and understanding of the impacts of the climate crisis and environmental disturbances on the dynamics of forests. The authors make the recommendation that ‘forest management must ultimately confront the elevated mortality and uncertainty in recruitment and growth when considering options for sustaining the societal benefits of forests into the future’. Thus the findings from this study should be used as a critical step forward in effectively managing the impacts of anthropogenic climate change on forests now and in the 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. 

Globally, abandoned agricultural land has become a pervasive phenomenon after years of unsustainable cultivation methods; among other factors, the use of chemical fertilisers has left land depleted to the point of no return. Initiatives to restore these lands to use as tools in the fight against the climate crisis are underway.


In some instances, however, abandoned agricultural land is still arable and perhaps never fully cultivated but it is found in marginal locations where the prospects of quality life of farmers are poor. One of the main reasons for the abandonment is urbanisation. As a result, currently, more agricultural land is being abandoned than converted to it, particularly in North America and Western Europe. The global footprint of agriculture has been decreasing while the production output has been increasing, made possible by the intensification of cultivation methods.             

In light of the world’s climate crisis, it has become clear that fossil fuels are not the only resources threatening the planet’s sustainability. Water, clean air and arable land to grow food for an ever-growing world population are becoming increasingly scarce, and if ‘business as usual’ outputs continue, the challenges will soon become insurmountable. 

The world’s population has grown from 2.6 billion in 1950 to 8 billion today and is predicted to hit 9.7 billion by 2050. Human use affects over 70% of all ice-free land and about 25% of this land is subject to human-induced degradation, which is also exacerbated by climate change. 

Therefore, it is intuitive that the solution is also to be found in man’s hands.

As Richard Conniff summarises in an article for Yale360, between 1997 and 2018 the US has lost 98 000 square miles of farmland. China reportedly loses 7 700 square miles of precious agricultural land each year. By 2040, abandoned land in the EU could amount to 82 000 square miles- 11% of the land actively farmed at the beginning of the century. 

By planting trees in those areas, 25% of anthropogenic CO2 could be sequestered from the atmosphere while retaining water and bringing fertility and community back to the land. According to a recent report by the Intergovernmental Panel for Climate Change (IPCC) currently ‘one quarter to one third of land’s potential net primary production for food, feed, fibre, timber and energy’ is being used.

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Abandoned Farmland Restoration

Many initiatives have been proposed and some put into practice successfully. There are examples of both large scale international projects, as well ‘grassroots’ approaches. One such global project- the Bonn Challenge– is a global effort to restore 350 million hectares of deforested and degraded land by 2030. The challenge also aims ‘to restore ecological integrity at the same time as improving human well-being through multifunctional landscapes’. It has been estimated that reaching the 2030 goal would generate USD 170 billion per year in net benefits from ‘watershed protection, improved crop yields and forest products, and could sequester up to 1.7 gigatonnes of carbon dioxide equivalent annually’.

A ‘grassroots’ example of these projects put into practice is the work of Dr Willie Smits in the forests of Kalimantan and Sulawesi, an island near Borneo. What Dr Smits has come to realise and articulate in his TED talk is that environmental degradation and environmental restoration differ only in the type and extent of human involvement in any projects which are beneficial to them, and affect the environment as a consequence.

This is the case particularly in developing countries where people are often willing to agree to environmental trade-offs for money (from selling land to foreign investors) or secure jobs (such as on oil palm plantations). 

Dr. Smits and his team from the Masarang Foundation developed an approach to restoration of degraded land into forests which the local community participates in and benefits from at all stages from planning to execution. The approach uses an integrated design wherein trees of valuable yield, such as the sugar palm, nitrogen-fixing plants, such as fodder, and other root and tree crops are planted in a grid sequence for maximum efficiency. This approach, focused on biodiversity, encourages the return of beneficial soil microbes and improves soil texture and the retention of nutrients and water. 

Not all land is suitable for reforestation and the data available  is largely confined to remote satellite sensing. This means that obtaining the larger picture does not distinguish between publicly and privately owned land, making the theory more complicated in practice. Additionally, initiatives are often poorly planned. For example, about 10% of countries participating in the Bonn Project have committed to reforest more land than they actually have available. Bearing in mind its limitations, this idea holds great potential for the future.

For successful restoration to take place, the end goal doesn’t always necessarily have to be a forest. A study published in Nature shows that in some cases grassland or savanna ecosystems are more optimal for carbon sequestration and storage because they are able to hold more carbon underground. These environments are also less prone to drought and fires.  

Abandoned land is able to naturally revert back to its original state on its own accord, as extensively described in Alan Weisman’s book The World Without Us. However, it can take hundreds of years for the land to regain its initial biodiversity and productivity. With the climate crisis pending and no more luxury of time, strategies for speeding up the process of regeneration are in demand. 

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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

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