My Science School

• The impact of sea-level rise includes flooding, habitat destruction and salt water intrusion in coastal areas, increased soil erosion and disappearance of low-lying islands. Rising sea levels also make storm surges capable of much greater damage. (Storm surge is the abnormal rise in seawater level during a storm. Storm surge can penetrate well inland.)


• Higher sea levels are coinciding with more hurricanes, contributing to more powerful storm surges that can strip away everything in their path.


• Saltwater intrusion is the flow of seawater into water bodies such as rivers and aquifers (underground water bearing rocks). It is a major concern as it can induce contamination of water resources, used for drinking, household purposes and agriculture. Increased salinity of coastal freshwater can threaten vegetation and wildlife of the region.


• Many birds use coastal ecosystems to find food, live and breed. Sea turtles lay their eggs on beaches, returning to the same location every year. When beaches erode, these animals and birds will be affected.


• Rising sea level will lead to the displacements of people. It could create 187 million climate refugees by 2100, according to a study.

 

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The rise in sea-levels is linked to two primary factors, both induced by global warming.

Thermal expansion:

The oceans are absorbing more than 90% of the increased atmospheric heat associated with greenhouse gas emissions. When water heats up, it expands. The ocean water expands to fill a greater volume and takes up more space. This is called thermal expansion, and it is responsible for one-third of the sea-level rise, according to studies.

Melting of glaciers and ice caps:

Warmer temperatures cause land-based ice such as glaciers and ice sheets to melt, and the meltwater flows into the ocean to increase sea level. Melting ice causes about two-thirds of the rise in sea level.

If all the ice in glaciers and sheets melt then the sea level would rise by 216 feet. That could cause some countries to disappear under the oceans. That’s a scenario scientists think would probably take many centuries, but it could eventually happen if the world keeps burning fossil fuels indiscriminately.

 

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A rise in sea level may put some of the Indian cities, including Mumbai, Chennai and Kolkata, in the flood-risk zone, and it could affect a total of 36 million people in the country by 2050, according to a research report by the New Jersey-based science organisation Climate Central. By 2100, this number could increase to 51 million. Parts of these coastal cities could be completely wiped out, the report said.

Showing that many of the world’s coastlines are now for lower than earlier, the report projected that worldwide, some 300 million people could be affected by 2050. The threat is particularly concentrated in six Asian countries: China, India, Vietnam, Thailand, Indonesia and Bangladesh.

Sea-level rise and flooding could have profound economic and political consequences within the lifetimes of people alive today, showed the findings of the study.

Even if emission is zero

According to another study published last month, the dramatic rise in sea levels will continue even if the world manages to slash greenhouse gas emissions to zero by 2030. Emissions between 2015 and 2030 would be enough to raise levels by 8 cm by 2100, according to research by experts based in Germany.

The average sea level is expected to swell by at least a metre by 2300 in the extremely unlikely event that greenhouse gas emissions fall to zero in the next 11 years.

If planets heats up further

In the worst-case scenario – in which the planet heats up by 5 degrees Celsius in the next 80 years – melted ice could raise sea levels worldwide by more than 6.5 feet, according to a study published in May 2019. That could result in a loss of 6,91,120 square miles of land, the report said. That’s an area larger than France, Germany, Spain and the U.K. combined.

The water could swamp major coastal cities such as New York and Shanghai. Small Pacific island nations such as Vanuatu would be rendered uninhabitable or disappear entirely.

In Earth’s geological past, sea level has risen and fallen dramatically. For instance, during the last Ice Age, ice covered the planet and sea level was at least 394 ft lower than what it is today. And during the Eocene – 40 million years ago, the Earth was almost ice-free and the sea level was around 230 ft higher than today.

These changes are part of Earth’s natural glacial cycles and have occurred over millions of years. But the current sea-level rise is caused mainly due to human activities.

The burning of fossil fuels, deforestation, decomposition of waste in landfills and livestock have released enormous amounts of greenhouse gases into the atmosphere. These emissions have caused the Earth’s surface temperature to rise, causing global warming, which directly contribute to sea-level rise.

 

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• During photosynthesis, trees absorb CO2 from the atmosphere, and store it as carbon for long time periods. At present, forest store as much as 45% of all land carbon. Deforestation affects this carbon cycle.


• Deforestation is considered to be one of the contributing factors to global warming and climate change. Trees absorb not only the carbon dioxide that we exhale, but also the heat-trapping greenhouse gases that human activities emit. With increase in deforestation, larger amount of these gases will enter the atmosphere and global warming will increase further. About 300 billion tonnes of carbon, 40 times the annual greenhouse gas emissions from fossil fuels, is stored in trees, according to Greenpeace.


• While fossil fuel combustion is the largest source of carbon dioxide emission, deforestation is the second largest. When trees die (or are cut or burnt), they release the stored carbon dioxide into the air.


• Forests release large quantities of water into the atmosphere via perspiration. This replenishes the clouds and triggers rain, which in turn, maintains the forests. When forests are destroyed, it affects rainfall and thereby causes drought.


• As much as 70% of the world’s plants and animals live in forests. They are losing their habitats due to deforestation. Loss of habitat can lead to species extinction. For instance, in Malaysia and Indonesia, Bornean rainforests are cut down to make way for producing palm oil. The effect of deforestation is so much that it is driving the extinction of orangutans, the world’s largest tree-dwelling great apes, native to the rainforests of Borneo and Sumatra. Removing trees deprives the forest of its canopy, which blocks the sun’s rays during the day and retains heat at night. That disruption leads to more extreme temperature swings that can, in turn, affect plants and animals.


• Trees roots stabilize the soil around the tree and hold them in place. When they are cut, the soil is free to wash or blow away, which can lead to soil erosion.


• Deforestation can also cause flooding. Coastal vegetation lessens the impact of waves and winds associated with a storm surge. Without this vegetation, coastal villages are susceptible to damaging floods.

 

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Deforestation is the destruction of forests in order to make the land available for other uses. The Earth loses 18.7 million acres of forests per year, which is equal to 27 football fields every minute, according to the World Wildlife Fund (WWF).

Common methods of deforestation are clear cutting and burning of trees. These methods leave the land completely barren. Clear cutting is when large swaths of land are cut down all at once. This sudden change causes severe damage to the ecosystem.

Cause of deforestation

• A major contributor to deforestation is the practice of slash-and-burn technique of farming. Farmers clear forest by cutting down trees, burn them and then grow crops in the soils fertilized by the ashes. Typically, the land produces for only a few years. The farmers abandon the area and move on to a new patch of land and begin the process again.


• Grazing of livestock, mining and drilling are the other major causes.


• Trees are also cut to be used as fuel.


• Forests are also cleared for housing and urbanisation; for industries, dams and other infrastructural projects.


• Wood is used in the making of paper, furniture and the construction of buildings. Some of the loggers act illegally. They also build roads to access more and more remote forests, and this leads to further deforestation.


• Not all deforestation is intentional. Some are caused by a combination of human and natural factors such as wildfires, which may prevent the growth of young trees.

 

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• In the concrete jungle that Mumbai is, Aarey Milk Colony is a treasured green patch. It has over 5, 00,000 trees. On October 4, 2019, when the Bombay High Court allowed the State government to go ahead with the felling of 2,600 trees to make space for a proposed Metro Rail car shed, the residents protested. But it was too late, as the Brihanmumbai Municipal Corporation (BMC) acted soon after the order and had already cut 1,500 trees (under the cover of darkness). The issue became bigger and uglier – clashes broke out between the police and environmental activists, leading to the arrest of at least 29 persons. Thea matter was taken to the Supreme Court and it, in a special hearing on October 7, 2019, ordered the BMC to halt the felling of trees in the Aarey forest. But it did not order the halt or shifting of the metro shed project from Mumbai’s Aarey in its subsequent hearing.


• In September, reports emerged that the Jharkhand’s Water Resources Department has approved the cutting of around 3.44 lakh trees in Jharkhand’s Palamau Tiger Reserve to make way for the North Koel reservoir, also known as Mandal dam. As per latest estimation, the reserve has nil tigers. However, the felling of so many trees will damage the ecosystem, warn wildlife experts. The reserve has already suffered significant damage because of the expansion of road and railway network.

Development projects such as these are among the top reasons for the deforestation. According to the central government statistics, between 2015 and 2018, about 20,000 hectares of forest land was cleared for development activities such as mining, thermal power plants, dams, roads, railways and irrigation projects. Under the Forest (Conservation) Act, 1980, forest areas can be diverted by the environment ministry for non-forestry purposes such as mining. To compensate, authorities should carry out afforestation at a different place. However, they are in no way a substitute the diverse and natural forests that have been lost permanently due to deforestation, say experts.

It is an irony that the world, while seeking to slow the pace of climate change on the one side, continues to cut down trees in large numbers on the other hand. Trees are part of the solution in our fight against climate change.

 

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An ecological footprint compares the total natural resources people consume with the land and water area that is required to replace these resources.

The ecological footprint works like an accounting balance sheet. On the minus side are the resource consuming activities like energy usage, logging, farming, fishing, etc. On the plus side is Earth’s bio capacity – its ability to replace these resources and absorb the waste.

The ecological footprint measures the demands humans place on Nature. It includes estimates of the sea and forest-covered land areas needed to absorb greenhouse gases like carbon dioxide. The more the greenhouse gases, the more the water and forest area required for absorbing them.

Thus a large carbon footprint would mean a larger ecological footprint. In short, the ecological footprint tells us how much of Earth is required to support human life if a particular lifestyle is followed.

Since the mid-1980s, humans have been consistently, leaving a larger ecological footprint. For example, for 2007 humanity’s ecological footprint was estimated at 1.5 Earths.

It means that humans consumed resources 1.5 times faster than Earth can reproduce them, the deficit was made up by drawing up on stored resources like fossil fuels which Earth does not replenish every year. The UN estimates that if current trends continue, by the mid-2030s we will need two Earths to sustain ourselves!

 

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