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The Holocene Epoch is the current period of geologic time. It relates to the global changes caused by human activity, and is said to have begun about 11.700 years ago after the icy Pleistocene ended. When the glaciers of the ice era retreated, Earth entered a period of warming. The landscape of the tundra changed, large mammals that had adapted to the extreme cold became extinct, and humans who hunted the mammoth mammals began exploring plant materials to supplement their diet. Climatic changes took place, the human population began to grow, and sadly, we began ushering in processes and inventions that would have serious implications on the future of the planet.

The classification of the geological time scale is done into the following: Eons, Eras, Periods, Epochs and Ages. In this timeline classification, Eons are divided into Eras, Eras are further divided into Periods, Periods divided into Epochs and the Epochs are further subdivided into Ages. Thus, Holocene is an Epoch classified under the Quaternary Period, which comes under the Cenozoic Era, which is classified under the Phanerozoic Eon.

Under the classification of the Quaternary Period, comes the Pleistocene Epoch and Holocene Epoch. The Holocene is the Epoch which follows the Plestocene Epoch. It is also identified as a warm period and an interglacial period by the geologists, and Earth scientists. The striking feature of the Holocene time scale is the rapid proliferation, growth, and the impacts of Human species. The Holocene is characterized by all of the written history, technological advancements, development of many civilizations, and the current transition towards urbanization of the human population. The influence of humans is predominant in this Epoch and the impact on modern-era Earth and the ecosystems have led to the classification of the Holocene. 

The Holocene Time-scale

The word Holocene finds its origin in the Ancient Greek language. Holocene meaning, according to Ancient Greek, is “whole new”. Breaking the word of Holocene into the Greek roots helps in identifying the holocene meaning. The term ‘Holo-’ is derived from the word Holos which means “whole”. The other ‘-cene’ is derived from the word kainos which means “new”.Thus, when combined together, the holocene meaning is “whole new”. The reasoning behind this, is the consideration that this epoch is entirely new as it is the most recent one and is still continuing. Also, the suffix ‘-cene’ is used for all the seven epochs that are classified under the Cenozoic Era. 

According to the International Commision on Stratigraphy, the Holocene started 11,650 calibrated years ago before present. The Holocene Epoch is further sub-divided into five time intervals based on climatic fluctuations, which are also known as the Chronozones:

Preboreal: This is the time period between 10 kiloannum (ka) years - 9 ka before present (BP) (present i.e. 195)). 
Boreal: This lies between 9 ka - 8 ka years BP
Atlantic: 8 ka to 5 ka years BP
Subboreal: 5 ka - 2.5 ka years BP
Subatlantic: 2.5 ka years BP.

During the time of the Holocene, there have been many changes that have taken place in terms of geology and climate which have shaped the current world. Also, the changes occurring due to Global warming in the last century itself has also impacted the natural progression of this Epoch. We will understand a few of these changes as we go through with the article.

Geological Changes During Holocene

The movements of the continent under the pressure of tectonic forces, has been less than a kilometre in the span of 10,000 years of Holocene. Another important change in the geology of the Earth, during this Epoch has been the rise in the sea-level. In the early part of the Holocene Epoch, because of the melting of ice, the sea-level rises about 35 m. In the later part of the Epoch also, the sea-level rises by another 30 m. Many of the areas of landmass above around 40 degrees North latitude that had been covered by ice of the Pleistocene Epoch were depressed by the weight of Ice. Hence, as the glacial period began to recede and the ice began to melt, the landmass rose by180 meters during the late Pleistocene and early Holocene Epoch. These landmasses still continue to rise. 

Climate Changes During Holocene

As such the climate changes have been stable over the Holocene when compared to the cold period of Glaciation. The records collected from the ice cores have shown that before the start of Holocene there was a time period of warming happening globally which began after the end of the last of the ice ages and the cooling periods. The climatic changes became more and more regional and during the transition from the late glacial to Holocene the cold reversal known as Huelmo-Mascardi, began from South America in the Southern Hemisphere and most of the warmth flowed from south to north about 11,000 to 7,000 years ago. It is thought that this happened because of the residual glacial ice which was left in the Northern Hemisphere.

Early Human Settlements During Holocene

The Mesolithic age began with the beginning of the Holocene in most of Europe. In the regions of Middle East and Anatolia a very early neolithisation and Epipaleolithic period began. During this period the cultures that began include Hamburgian, Federmesser and Natufian culture. Also, some of the oldest inhabited places that are still existing such as the Tell es-Sultan (Jericho) in the Middle East began to be first settled. Other evidence of such settlements are given by archaeology at locations of Göbekli Tepe where proto-religion first began as long as 9th millennium BCE. Since then human courses have taken the known developments and continue till date.

It is noteworthy that, using terms like Holocene period, Holocene era or Holocene age, can be confusing as the terms period, era and age have different and definite meaning under the Geographical Time Scale classification system Hence, using Holocene or Holocene Epoch is more reliable and justifiable under such circumstances. 

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The long-term heating up of the planet due to human activity since the 19th century pre-industrial era is called global warming. One of the main causes driving global warming is the burning of fossil fuels which increases the level of heat-trapping greenhouse gases in the atmosphere. Research has pointed out that human activities have increased the earth's average temperature by about 1 degree Celsius. From the atmosphere to ocean and land, the temperature is rising. The figure is projected to increase with every passing decade. Rising temperatures can impact sea level, thaw glaciers, affect rainfall patterns and lead to extreme events such as hurricanes, flash floods and tomados.

What causes global warming?

 Global warming occurs when carbon dioxide (CO2) and other air pollutants collect in the atmosphere and absorb sunlight and solar radiation that have bounced off the earth’s surface. Normally this radiation would escape into space, but these pollutants, which can last for years to centuries in the atmosphere, trap the heat and cause the planet to get hotter. These heat-trapping pollutants—specifically carbon dioxide, methane, nitrous oxide, water vapor, and synthetic fluorinated gases—are known as greenhouse gases, and their impact is called the greenhouse effect.

Though natural cycles and fluctuations have caused the earth’s climate to change several times over the last 800,000 years, our current era of global warming is directly attributable to human activity—specifically to our burning of fossil fuels such as coal, oil, gasoline, and natural gas, which results in the greenhouse effect. In the United States, the largest source of greenhouse gases is transportation (29 percent), followed closely by electricity production (28 percent) and industrial activity (22 percent).

Curbing dangerous climate change requires very deep cuts in emissions, as well as the use of alternatives to fossil fuels worldwide. The good news is that countries around the globe have formally committed—as part of the 2015 Paris Climate Agreement—to lower their emissions by setting new standards and crafting new policies to meet or even exceed those standards. The not-so-good news is that we’re not working fast enough. To avoid the worst impacts of climate change, scientists tell us that we need to reduce global carbon emissions by as much as 40 percent by 2030. For that to happen, the global community must take immediate, concrete steps: to decarbonize electricity generation by equitably transitioning from fossil fuel–based production to renewable energy sources like wind and solar; to electrify our cars and trucks; and to maximize energy efficiency in our buildings, appliances, and industries.

How is global warming linked to extreme weather?

 Scientists agree that the earth’s rising temperatures are fueling longer and hotter heat waves, more frequent droughts, heavier rainfall, and more powerful hurricanes.

In 2015, for example, scientists concluded that a lengthy drought in California—the state’s worst water shortage in 1,200 years—had been intensified by 15 to 20 percent by global warming. They also said the odds of similar droughts happening in the future had roughly doubled over the past century. And in 2016, the National Academies of Science, Engineering, and Medicine announced that we can now confidently attribute some extreme weather events, like heat waves, droughts, and heavy precipitation, directly to climate change.

The earth’s ocean temperatures are getting warmer, too—which means that tropical storms can pick up more energy. In other words, global warming has the ability to turn a category 3 storm into a more dangerous category 4 storm. In fact, scientists have found that the frequency of North Atlantic hurricanes has increased since the early 1980s, as has the number of storms that reach categories 4 and 5. The 2020 Atlantic hurricane season included a record-breaking 30 tropical storms, 6 major hurricanes, and 13 hurricanes altogether. With increased intensity come increased damage and death. The United States saw an unprecedented 22 weather and climate disasters that caused at least a billion dollars’ worth of damage in 2020, but 2017 was the costliest on record and among the deadliest as well: Taken together, that year's tropical storms (including Hurricanes Harvey, Irma, and Maria) caused nearly $300 billion in damage and led to more than 3,300 fatalities.

The impacts of global warming are being felt everywhere. Extreme heat waves have caused tens of thousands of deaths around the world in recent years. And in an alarming sign of events to come, Antarctica has lost nearly four trillion metric tons of ice since the 1990s. The rate of loss could speed up if we keep burning fossil fuels at our current pace, some experts say, causing sea levels to rise several meters in the next 50 to 150 years and wreaking havoc on coastal communities worldwide.

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All living things need food to live and grow, and creatures eat more than one variety of plant or animal. Food chain is the sequence in which matter and energy in the form of food gets transferred from one organism to another. Unless another there is enough food available to all living organisms, their survival and the stability of the environment cannot be ensured. The prey species binge on plant life in their habitat while the predators control the prey population and outbreak of diseases. Any change in the chain can cause a ripple effect. The prey-predator relationship in many ecosystems has become complex in recent times due to threats such as global warming. climate change and loss of habitat.

There are four main elements of the food chain:

1. The Sun: The sun is the planet's primary energy source, powering everything else.

2. The producers: All autotrophs, such as phytoplankton, cyanobacteria, algae, and green plants, are producers in a food chain. A food chain starts here. The food chain begins with the farmers and ranchers. To create food, the producers make use of solar energy. Autotrophs, who produce their own food, are another term for producers. Any plant or creature that has its own nutrition through photosynthesis is a producer. Green plants, phytoplankton, and algae, for instance, are food chain producers.

3. The consumers: All creatures that depend on plants or other organisms for nutrition are considered consumers. This is the most critical component of the food chain since it includes nearly all species of living creatures. Herbivores consume plants, carnivores eat other animals, parasites survive on other creatures by damaging them, and scavengers devour dead animals' corpses, all of which are included in the animal kingdom.

4. The decomposers: Decomposers are creatures that get energy from dead or discarded organic material. This is the final level of the food chain. Decomposers are essential components of the food chain because they transform organic waste into inorganic materials such as nutrient-rich soil or land.

Decomposers aid in nutrient recycling by supplying nutrients to soil or seas that autotrophs or producers may use. As a result, a completely new food chain is formed.

Food Chain Types

Food chains are classified into two types: detritus food chains and grazing food chains. Let's study them in detail:

1. Detritus food chain:
The detritus food chain includes many creatures and plants such as bacteria, protozoa fungus, algae, insects, mites, and worms. The detritus food chain begins with decomposing organic matter. Food energy is transferred to decomposers and detritivores, which are then consumed by smaller creatures such as predators. Carnivores, such as maggots, become prey for larger carnivores such as frogs, snakes, and so on. Primary consumers, such as fungus, bacteria, and protozoans, are detritivores that feed on detritus.

2. Grazing food chain:
The grazing food chain is a sort of food chain that begins with green plants and progresses via herbivores and predators. Photosynthesis provides energy to the lowest trophic level in a grazing food chain.
The initial energy transmission in this sort of food chain occurs from plants to herbivores. This food chain is based on the transfer of energy from autotrophs to herbivores. Because autotrophs constitute the foundation of all ecosystems on Earth, most ecosystems on the planet follow this type of food chain.

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Fossil fuels are formed from decomposed plants and animals that lay buried deep inside the earth for millions of years. With the progress of time, heat and pressure turn these remains into fossil fuels. The most common ones are coal, crude oil (petroleum) and natural gas. They have multiple uses (from generating electricity and powering vehicles and planes to heating homes). Fossil fuels are nonrenewable and can harm the environment since the carbon stored in them gets released into the atmosphere as carbon dioxide, a greenhouse gas that causes global warming.

According to the National Academies of Sciences, 81 percent of the total energy used in the United States comes from coal, oil, and natural gas. This is the energy that is used to heat and provide electricity to homes and businesses and to run cars and factories. Unfortunately, fossil fuels are a nonrenewable resource and waiting millions of years for new coal, oil, and natural gas deposits to form is not a realistic solution. Fossil fuels are also responsible for almost three-fourths of the emissions from human activities in the last 20 years. Now, scientists and engineers have been looking for ways to reduce our dependence on fossil fuels and to make burning these fuels cleaner and healthier for the environment.

Scientists across the country and around the world are trying to find solutions to fossil fuel problems so that there is enough fuel and a healthy environment to sustain human life and activities in the future. The United States Department of Energy is working on technologies to make commercially available natural-gas-powered vehicles. They are also trying to make coal burning and oil drilling cleaner. Researchers at Stanford University in California have been using greener technologies to figure out a way to burn fossil fuels while lessening their impact on the environment. One solution is to use more natural gas, which emits 50 percent less carbon dioxide into the atmosphere than coal does. The Stanford team is also trying to remove carbon dioxide from the atmosphere and store it underground—a process called carbon capture and sequestration. Scientists at both Stanford and the University of Bath in the United Kingdom are trying something completely new by using carbon dioxide and sugar to make renewable plastic.

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The dying out or extermination of a species is what is referred to as extinction. When species are diminished because of environmental factors or because of evolutionary changes in their members, extinction occurs. While rates of extinction have varied largely, human activities, deforestation, habitat loss, over-hunting, pollution and climate change have meant that the present-day extinction rate is many times more than what it was previously.

About 541 million years ago, a great expansion occurred in the diversity of multicellular organisms. Paleobiologists, scientists who study the fossils of plants and animals to learn how life evolved, call this event the Cambrian Explosion. Since the Cambrian Explosion, there have been five mass extinctions, each of which is named for the geological period in which it occurred, or for the periods that immediately preceded and followed it.

The first mass extinction is called the Ordovician-Silurian Extinction. It occurred about 440 million years ago, at the end of the period that paleontologists and geologists call the Ordovician, and followed by the start of the Silurian period. In this extinction event, many small organisms of the sea became extinct. The next mass extinction is called Devonian extinction, occurring 365 million years ago during the Devonian period. This extinction also saw the end of numerous sea organisms.

The largest extinction took place around 250 million years ago. Known as the Permian-Triassic extinction, or the Great Dying, this event saw the end of more than 90 percent of the Earth’s species. Although life on Earth was nearly wiped out, the Great Dying made room for new organisms, including the first dinosaurs. About 210 million years ago, between the Triassic and Jurassic periods, came another mass extinction. By eliminating many large animals, this extinction event cleared the way for dinosaurs to flourish. Finally, about 65.5 million years ago, at the end of the Cretaceous period came the fifth mass extinction. This is the famous extinction event that brought the age of the dinosaurs to an end.

In each of these cases, the mass extinction created niches or openings in the Earth’s ecosystems. Those niches allowed for new groups of organisms to thrive and diversify, which produced a range of new species. In the case of the Cretaceous extinction, the demise of the dinosaurs allowed mammals to thrive and grow larger.

Scientists refer to the current time as the Anthropocene period, meaning the period of humanity. They warn that, because of human activities such as pollution, overfishing, and the cutting down of forests, the Earth might be on the verge of—or already in—a sixth mass extinction. If that is true, what new life would rise up to fill the niche that we currently occupy?

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A climate pattern describing the unusual warming of surface waters in the easter tropical Pacific Ocean, El Nino corresponds to the warm phase of the larger phenomenon known as the El Nino-Southern Oscillation (ENSO). The pattern that describes the unusual cooling of the region's surface waters, or the cool phase of ENSO, is referred to as La Nina. Ocean temperatures, the speed and strength of ocean currents, health of local fisheries, and the local weather of regions from Australia to South America and beyond are affected by the El Nino, which is not a regular cycle.

The El Nino phenomenon caused muddy rivers to overflow along the entire Peruvian coast in 2017.

El Nino can be understood as a natural phenomenon wherein the ocean temperatures rise especially in parts of the Pacific ocean. It is the nomenclature which is referred to for a periodic development along the coast of Peru. This development is a temporary replacement of the cold current along the coast of Peru.   El Nino is a Spanish word. The term El Nino basically means ‘the child’. This is due to the fact that this current starts to flow around Christmas and hence the name referring to baby Christ.

Another natural phenomenon, similar to El Nino is La Nina, which is also in news these days. The term La Nina literally means ‘ little girl’. It is termed as opposite to the phenomenon of El Nino as it results in the ‘cooling’ of the ocean water in parts of the Pacific ocean.   Both of them also result in changes in atmospheric conditions along with oceanic changes.

El Nino Effects

El Nino results in the rise of sea surface temperatures
It also weakens the trade winds of the affected region
In India, Australia, it can bring about drought conditions. This affects the crop productivity largely. It has been also observed certain times, that EL Nino may not bring drought but cause heavy rainfall. In both the cases, it causes heavy damage.
However, in some other countries it may result in a complete reversal, i.e., excessive rainfall.

 Mitigation Of  Effects:

Keeping a check on the sea surface temperatures.
Maintaining sufficient buffer stocks of food grains and ensuring their smooth supply.
Ensuring relevant support to the farmer community including economic help.
Alternative ways to be promoted such as the practice of sustainable agriculture.

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A geographic area where plants, animals, and other organisms, along with weather and landscape, work together to form a sphere of life is known as an ecosystem. Ecosystems thus contain biotic or living parts like plants, animals and other organisms as well as abiotic factors like temperature, humidity and rocks. The interdependence of these various parts and factors. either directly or indirectly, is what makes ecosystems thrive.

Ecosystems are controlled by external and internal factors. External factors such as climate, parent material which forms the soil and topography, control the overall structure of an ecosystem but are not themselves influenced by the ecosystem. Internal factors are controlled, for example, by decomposition, root competition, shading, disturbance, succession, and the types of species present. While the resource inputs are generally controlled by external processes, the availability of these resources within the ecosystem is controlled by internal factors. Therefore, internal factors not only control ecosystem processes but are also controlled by them.

Ecosystems are dynamic entities—they are subject to periodic disturbances and are always in the process of recovering from some past disturbance. The tendency of an ecosystem to remain close to its equilibrium state, despite that disturbance, is termed its resistance. The capacity of a system to absorb disturbance and reorganize while undergoing change so as to retain essentially the same function, structure, identity, and feedbacks is termed its ecological resilience. Ecosystems can be studied through a variety of approaches—theoretical studies, studies monitoring specific ecosystems over long periods of time, those that look at differences between ecosystems to elucidate how they work and direct manipulative experimentation. Biomes are general classes or categories of ecosystems. However, there is no clear distinction between biomes and ecosystems. Ecosystem classifications are specific kinds of ecological classifications that consider all four elements of the definition of ecosystems: a biotic component, an abiotic complex, the interactions between and within them, and the physical space they occupy.

Ecosystems provide a variety of goods and services upon which people depend. Ecosystem goods include the "tangible, material products" of ecosystem processes such as water, food, fuel, construction material, and medicinal plants. Ecosystem services, on the other hand, are generally "improvements in the condition or location of things of value". These include things like the maintenance of hydrological cycles, cleaning air and water, the maintenance of oxygen in the atmosphere, crop pollination and even things like beauty, inspiration and opportunities for research. Many ecosystems become degraded through human impacts, such as soil loss, air and water pollution, habitat fragmentation, water diversion, fire suppression, and introduced species and invasive species. These threats can lead to abrupt transformation of the ecosystem or to gradual disruption of biotic processes and degradation of abiotic conditions of the ecosystem. Once the original ecosystem has lost its defining features, it is considered "collapsed". Ecosystem restoration can contribute to achieving the Sustainable Development Goals.

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The process by which natural or human causes reduce the biological productivity of drylands (arid, semi-arid and dry sub-humid areas) is known as desertification, also referred to as desertization. Climate change, deforestation, overgrazing, unsustainable irrigation practices, political instability, poverty, or a combination of these factors generally result in declines in productivity of drylands. Africa has been the continent that is most affected by desertification.

Desertification, in short, is when land that was of another type of biome turns into a desert biome because of changes of all sorts. A huge issue that many countries have is the fact that there are large pockets of land that are going through a process that is known as desertification.

Desertification affects topsoil, groundwater reserves, surface runoff, human, animal, and plant populations. Water scarcity in drylands limits the production of wood, crops, forage, and other services that ecosystems provide to our community.

According to UNESCO, one-third of world’s land surface is threatened by desertification, and across the world, it affects the livelihood of millions of people who depend on the benefits of ecosystems that drylands provide. 

Various Causes of Desertification

1. Overgrazing

Animal grazing is a huge problem for many areas that are starting to become desert biomes. If there are too many animals that are overgrazing in certain spots, it makes it difficult for the plants to grow back, which hurts the biome and makes it lose its former green glory.

2. Deforestation

When people are looking to move into an area, or they need trees in order to make houses and do other tasks, then they are contributing to the problems related to desertification. Without the plants (especially the trees) around, the rest of the biome cannot thrive.

3. Farming Practices

Some farmers do not know how to use the land effectively. They may essentially strip the land of everything that it has before moving on to another plot of land. By stripping the soil of its nutrients, desertification becomes more of a reality for the area that is being used for farming.

4. Excessive Use of Fertilizers and Pesticides

The use of excessive amounts of fertilizers and pesticides to maximize their crop yields in the short term often leads to significant damages for the soil.

In the long run, this may turn from arable into arid land over time, and it will no longer be suitable for farming purposes after a few years of excessive farming since the soil has been damaged too much over time.

5. Overdrafting of groundwater

Groundwater is the freshwater found underground and also one of the largest water sources. Over drafting is the process in which groundwater is extracted in excess of the equilibrium yield of the aquifer that is pumping or the excessive pulling up of groundwater from underground aquifers. Its depletion causes desertification.

6. Urbanization and Other Types of Land Development

As mentioned above, development can cause people to go through and kill plant life. It can also cause issues with the soil due to chemicals and other things that may harm the ground. As areas become more urbanized, there are fewer places for plants to grow, thus causing desertification.

7. Climate Change

Climate change plays a huge role in desertification. As the days get warmer and periods of drought become more frequent, desertification becomes more and more eminent.

Unless climate change is slowed down, huge areas of land will become desert; some of those areas may even become uninhabitable as time goes on.

8. Stripping the Land of Resources

If an area of land has natural resources like natural gas, oil, or minerals, people will come and mine it or take it out. This usually strips the soil of nutrients, which in turn kills the plant life, and eventually leads to the process of becoming a desert biome as time goes on.

There are some cases where the land gets damaged because of natural disasters, including drought. In those cases, there isn’t a lot that people can do except work to try and help rehabilitate the land after it has already been damaged by nature.

8. Soil Pollution

Soil pollution is a significant cause of desertification. Most plants are quite sensitive to their natural living conditions. When soil becomes polluted due to various human activities, the respective area of land may suffer from desertification in the long run. Higher the level of pollution more will be the degradation of soil over time.

9. Overpopulation and excessive consumption

Since our world population is continuously growing, the demand for food and material goods is also increasing at an alarming rate. Our overall level of consumption is also increasing at a steady rate.

Thus to fulfill our demand, we have to optimize our farming processes to harvest even higher crop yields. However, this excessive optimization of farming will hurt the soil and will eventually turn into the desertification of land in the long run.

10. Mining

Mining is another big reason for desertification. Large amounts of resources have to be extracted by industries to meet our demand for material goods. For mining, large areas of land have to be used, which causes deforestation as well as pollution of the nearby areas.

By the time most of the natural resources have been extracted, and mining practices are no more profitable, the soil gets damaged significantly, and the land becomes arid, which may not be recoverable, and desertification occurs.

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The long-term shifts in temperature and weather patterns is referred to as climate change. While these shifts have been natural for the longest period of humanity, human activities have become the main driver of climate change since the 1800s. This is mainly due to the burning of fossil fuels like coal oil and gas, which then produces heat-trapping gases to alter the delicate equilibrium governing the Earth in a negative fashion.

What Causes Climate Change?

There are lots of factors that contribute to Earth’s climate. However, scientists agree that Earth has been getting warmer in the past 50 to 100 years due to human activities.

Certain gases in Earth’s atmosphere block heat from escaping. This is called the greenhouse effect. These gases keep Earth warm like the glass in a greenhouse keeps plants warm.

Human activities — such as burning fuel to power factories, cars and buses — are changing the natural greenhouse. These changes cause the atmosphere to trap more heat than it used to, leading to a warmer Earth.

When human activities create greenhouse gases, Earth warms. This matters because oceans, land, air, plants, animals and energy from the Sun all have an effect on one another. The combined effects of all these things give us our global climate. In other words, Earth’s climate functions like one big, connected system.

Thinking about things as systems means looking for how every part relates to others. NASA’s Earth observing satellites collect information about how our planet’s atmosphere, water and land are changing.

By looking at this information, scientists can observe how Earth’s systems work together. This will help us understand how small changes in one place can contribute to bigger changes in Earth’s global climate.

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Biodiversity is the name we give to the variety of all life on Earth. Bacteria to baboons, plants to people - the range of life on our planet is incredible.

All living things exist within their own communities, or ecosystems - oceans, forests, deserts, ice caps and even cities. All this put together is biodiversity: the volume of life on Earth as well as how different species interact with each other and with the physical world around them.

The word biodiversity is a contraction of 'biological diversity'. The concept is broad and complex, but that complexity is what makes Earth a perfect place for humans to live.

Biodiversity and species richness

When we talk about biodiversity, we often talk about species richness as well. Species richness is the number of different species in an area, a way of measuring biodiversity.

Studying species richness helps us to understand the differences between places and areas.

For example, the Amazon rainforest very species-rich as it is home to 10 million species. In contrast, the Sahara Desert is far less rich, with just a few thousand species.

About 1.5 million species have been described by scientists, and most of them are insects. But it is thought that there are millions more sharing our planet with us.

Endangered species and mass extinction

Overall biodiversity loss can speed up extinction. More and more animals and plants are facing an uncertain future.

The International Union for Conservation of Nature (IUCN) is the global authority on the status of the natural world. It keeps a Red List of endangered species, an important indicator of the health of the world's biodiversity.

Currently, more than 30,000 species are listed as threatened with extinction, which is 27% of all assessed species.

We know that millions of species have already gone extinct over the long history of planet Earth. Biodiversity rates have always ebbed and flowed. In fact, at least 99% of all the organisms that have ever lived are now extinct. Researchers agree that five huge mass extinction events have already happened, including the one that wiped out the dinosaurs 66 million years ago.

However, extinction rates have been accelerating as human populations continue to grow, and many scientists argue we are living through a sixth mass extinction. This time, humans rather than natural events are to blame. Species diversity in more than half of land ecosystems is now critically low.

A 20% drop is widely considered the threshold at which biodiversity's contribution to ecosystem services is compromised. It's estimated that over a quarter of Earth's land surface has already exceeded this.

Causes of biodiversity loss

Biodiversity is in trouble in the UK and across the globe, and its loss can refer to local and worldwide extinctions. Species and ecosystems can be fragile, so small changes can have large consequences.

The causes of biodiversity loss are complicated, but we know the human population is making the problems worse.

In the short time humans have been on the planet we have increasingly disrupted the balance of biodiversity through changing land use, overexploitation of resources and the impact we are having on climate.

We are converting natural habitats into farms, factories, roads and cities. In the ocean, we are overfishing, drilling and mining.

Cities and towns have a smoothing effect on biodiversity, tending to favour generalist species like feral pigeons. Those that require a particular habitat, or are intolerant of disturbance or pollution, often can't survive. This is called biotic homogenization.

Animals and plants that can only live in one small area of land - like unique butterflies or flowers - can go locally extinct if the city's conditions are unfavorable to them.

A lichen specimen held in the crypt herbarium at the Museum. All living things, including plants and fungi, are represented by the word 'biodiversity'.

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Pollution is considered to be one of the world's biggest environmental threats. Here are ten shocking facts about pollution.

1. Plastic pollution adversely affects marine life. Over 1 million seabirds and 1,00,000 sea mammals are killed by plastic litter in the oceans every year.
2. In January 2019, the Ministry of Environment. Forest and Climate Change (MOEFCC) launched the National Clean Air Programme (NCAP) to monitor and curb air pollution around the country. It aims to reduce air pollution in 122 cities by 20-30 per cent by 2024.
3. According to the World Air Quality Report, 2020' released by the Swiss organisation, IQAir, New Delhi is the most polluted capital city in the world. Altogether 35 Indian cities are among the world's top 50 most polluted cities.
4. River Ganga flows through many urban centres such as Kanpur, Patna and Kolkata, which dump their industrial effluents and wastewater in the river. The entire length of the river is polluted by the presence of faecal coliform bacteria (germs found in the faeces of warm-blooded animals and humans), making its waters unfit for bathing and drinking.
5. About 70% of water sources in India are severely contaminated. Every year about 37.7 million Indians are affected by waterborne diseases.
6. Noise pollution is one of the most under-rated forms of pollution. According to the World Health Organization (WHO), noise above 65 decibels (dB) is termed as noise pollution. Sounds becomes harmful when its exceeds 75 decibels (dB) and painful when it is above 120 dB.
7. Only 20% of about 3.5 million tonnes of solid waste that our world generates every day is recycled, thus overwhleming the landfills with unmangable quantities. Waste is often disposed of at hazardous open dump sites in developing nations including India causing land pollution. Indiscriminate use of chemical fertilizers and pesticides has led to degradation of soil. making it infertile.
8. According to the WHO, air pollution kills about seven million people worldwide every year. Almost all of the global population (99%) breathe air that contains high levels of pollutants.
9. 80% of the world's wastewater is released back into the environment-most of it untreated, in the developing countries. Farm runoffs containing minerals such as nitrogen and phosphurus causes nutrient pollution leading to algae bloom. This destroys marine life and even results in permanent 'dead zones.
10. The Asian Brown Cloud (ABC) is a dense fog of pollutants that blankets South Asia from November to April. It hovers over western China, northwest Pakistan, Afghanistan and the Indo-Gangetic plain in northern India. The cloud is almost three kilometres thick. It contains a deadly cocktail of aerosols, ash, soot and other particles, 80 per cent of which is caused by human activity.

Picture Credit : Google 

What is the furthest down humans have gone? What is the Kola superdeep Borehole? Read on to find the answers.

In Jules Verne's science fiction novel, Journey to the Centre of the Earth (1864), three men reach the centre of the Earth. Is this ever possible? Our planet is made up of three main layers- the crust, the mantle and the core. The continents and oceans are situated on the crust which is about 8 km thick under the oceans and between 35 and 40 km deep under the continents. Below the crust is the mantle which is about 2,900 km thick. Next comes the core. The outer core, about 2.250 km thick, is made up of melted iron and nickel, and contained within it, is a ball-shaped inner core believed to be made up of solid iron and nickel.

The centre of the innermost core is the centre of the Earth. So there are thousands of kilometres to descend to reach the centre of the Earth, and what is the furthest down we've gone? When the Russians and the Americans were engaged in a race to the moon several decades ago, they also embarked on a race to inner space to see how far down they could go. While the Americans did not make much headway in this race downwards (Project Mohole'), the Russians went at it, hammer and tongs, in the Kola Peninsula and dug a hole 12.262 km deep over a period of 24 years from 1965 to 1989. They wanted to go at least 15 km down,  but just could not. This is the closest we've been able to go to the centre of the Earth. The Kola Superdeep Borehole, as it is now called, attracts curious visitors from around the world.

Picture Credit : Google