Ulan Bator is not only one of the coldest capitals on earth, it's also a city with massive air pollution. During the winter months, yurts like Tsegi’s are heated with coal and wood which contributes up to 70 percent of the smog in the city. Air pollution in Ulan Bator is seven times higher than what is considered safe by the WHO.

The Chinese capital has been suffering from smog so heavy that scientists say the city is almost uninhabitable - although it is home to 20 million people. Models suggest that 3.5 million people die globally every year because of air pollution - almost half of them in China. Having said this, it might be a surprise to learn that smog is an even bigger problem in other cities across the world.

Air pollution is one of Pakistan's main environmental concerns. The situation is particularly dramatic in the country's second largest city, Lahore. The smog is caused primarily by the high volume of road traffic, rubbish incineration and dust from the surrounding deserts.

In the nearly 10 million-strong city of New Delhi, the number of cars has increased from 180,000 to 3.5 million in the last 30 years. Still, it's the city's coal powered plants that are causing the biggest problem. They contribute to around 80 percent of the total air pollution in the city.

Sandstorms, like here in Riyadh, can contribute to smog forming because they increase the amount of particles in the air. In a place like Saudi Arabia, the intense ultra-violet rays also transform transport and industry emissions into ozone.

The poor air quality in Cairo causes a number illnesses among city residents, like chronic respiratory problems and lung cancer. The reason for the air pollution is an increase in road traffic and the booming industrial sector.

According to a study by the Max-Planck Institute in Mainz, some 15,000 people die every year in Dhaka due to air pollution. Researchers found the world's highest concentration of sulfur dioxide there.

Even if it looks the same the world over, smog is different, depending on the city. Smog in Moscow, for instance, is characterized by high amounts of hydrocarbons. The westerly winds which regularly plow across Moscow mean that the western part of the city generally has better air quality.

The smog in Mexico City is made worse by the geographical location. The city is surrounded on three sides by mountains. Due to the high levels of sulfur dioxide and hydrocarbons in the air, Mexico City was long considered one of the most polluted cities in the world. The situation is now improving due to new transport policies and certain factories being shut down.

In 2013, clearing practices were intensified again in Brazil’s rainforest. At the World Climate Summit in Warsaw, Brazil’s environment minister Izabella Teixeira admitted that by November this year, some 5,843 square kilometers of forest had been cut down. 2012 saw a loss of 4,571 square kilometers. In 2004, some 27,000 square kilometers went up in flames – a global negative record.

Intensified soy and wheat cultivation are partly to blame for the destruction of the rainforest. Brazil’s Para state saw the heaviest clearing. Destruction there rose by 136 percent between August 2012 and June 2013, according to the Imazon Institute. Near the city of Novo Progresso alone, some 400 hectares of forest were torched.

Even though only about five percent of Brazil’s 200 million inhabitants live in the Amazon region, dam construction is on the rise there. The Teles Pires hydropower plant on the Amazon tributary of the same name is due to start operation in 2015. So far, only one percent of the region’s hydropower potential is being used. Brazil’s national energy plan foresees a considerable rise by 2030.

Once it is cleared, the timber is sold. The illegally cleared areas in the Amazon region are often used by cattle breeders as pasture land. According to Brazilian law, they can become the rightful owners if they use the area ‘productively’ for five years in a row. The costs of clearing a forested area are estimated at around 3,000 euros (4,040 US dollars) per hectare.

This settler has been caught red-handed by the police. He illegally cut down trees in Jamanxim National Park. Brazil’s environment agency, Ibama, regularly patrols the Amazon’s national parks and nature reserves. In 2012, the agency issued fines of roughly half a billion euros. This year, the figure is likely to be even higher.

Last year, the Brazilian government announced it would limit the destruction of the rainforest until 2020 to less than 4,000 square kilometers per year by increasing patrols. But an ever-growing number of trees is lost to lumberjacks, gold diggers and agricultural companies. The illegally felled jungle giant pictured here was discovered near the city of Novo Progresso in Jamanxim National Park.

The 3,000-kilometer ‘Transamazonica’ highway was supposed to connect Brazil with its Latin American neighbors, Peru and Bolivia. But forty years after the ground was broken on Brazil’s famous federal highway BR 230, the gigantic project is still not finished. And environmental groups don’t want that to change.

Humble bars along the 'Transamazonica,' like this one, are the first port of call for truck drivers and those seeking their luck in the jungle. In the rainy season, the highway often turns into an impassable mud track. Small farmers and gold prospectors have settled along the gash cut through the jungle, pushing out the original inhabitants from their traditional areas of settlement.

The gold rush is threatening their lives. Hundreds of Yanomami have died from diseases brought into their areas by prospectors. Settlers invade the area regularly because the Yanomami’s reservation hosts big gold reserves. In June this year, the Brazilian army destroyed illegal airstrips in the nearly 9.5 million hectare reservation on the border with Venezuela.

Black gold: In the middle of the 'Alto Rio Guama' reservation, jungle giants like these disappear in round ovens. The illegally felled trees are turned into charcoal. This aerial image was taken from a police helicopter during a patrol in September 2013. The reservation belongs to the 'Nova Esperanca do Piria' community in Brazil's Para state.

The American black bear is one of more than 22,000 species threatened with extinction. During the past century, animals have been disappearing about 100 times faster than they used to, scientists from different American universities warned in a new study. According to the WWF, around 70 species go extinct every day.

According to the International Union for Conservation of Nature - which publishes a "red list" of threatened and endangered species - 41 percent of amphibian species and 26 percent of mammals are facing extinction. This Titicaca water frog, found only in Lake Titicaca in South America, used to be present in the millions in the early 1970s. By now, they have disappeared almost completely.

The causes of species loss are mostly manmade. They range from climate change, to pollution, to deforestation and beyond. About 2,000 trees have been cut down every minute during the past 40 years, according to a different study.

The world is embarking on its sixth mass extinction event, the current study concludes. The modern rate of species loss was compared to "natural rates of species disappearance before human activity dominated." The dodo (pictured above) was pushed to extinction by the introduction of nonnative species in 1690 - only 100 years after it had been discovered on Mauritius.

The study is based on documented extinctions of vertebrates - or animals with internal skeletons - from fossil records and other historical data. These results are estimations, since humans don't know exactly what happened throughout the course of Earth's history. In earlier extinction events, such as the Ice Age, only two out of 10,000 mammals died out per century - such as this primordial horse.

As species disappear, so do crucial services, such as pollination of crops by honeybees. At the current rate of species loss, humans will lose innumerable biodiversity benefits within three generations, the study's authors write. "We are sawing off the limb that we are sitting on," wrote author Paul Ehrlich from Stanford University.

If the current rate of extinction is allowed to continue, "life would take many millions of years to recover and our species itself would likely disappear early on," wrote lead author Gerardo Ceballos of the Universidad Autonoma de Mexico.

The study calls for "rapid, greatly intensified efforts to conserve already threatened species, and to alleviate pressures on their populations - notably habitat loss, over-exploitation for economic gain and climate change." In the meantime, the researchers hope their work will contribute to conservation, the maintenance of ecosystem services and biodiversity-oriented public policy.

The number of organisms living in a handful of soil outnumber all humans on the planet. They ensure that the humus layer stores nutrients and water. After oceans, soils represent the planet's largest carbon bank. Soils store more carbon than all the world's forests combined.

As cities around the world expand, fertile land is disappearing under concrete and asphalt. Microorganisms are suffocated under this artificial surface, and above it rainwater flows away rather than seeping into the soil.

Like human skin, the Earth's sensitive surface needs protection from the sun, wind and cold. Large areas can dry out, and ploughing can dislodge the top layer so that it is blown away by the wind.

Depletion of the soil through deforestation, over-fertilization and overgrazing can turn land into desert. Climatic factors like drought become a catalyst in a chain reaction - that is set in motion by human activity.

Monoculture plantations need large amounts of fertilizer and pesticides to remain productive. Some types of pesticides also harm the natural soil biota, reducing the soil's fertility.

Whether resulting from industrial leakage, disaster or weapons, or from years of over-fertilization: once soil is contaminated, fixing the damage is costly and time-consuming. According to official sources in China, nearly one-fifth of agricultural land there is contaminated.

The earth is also dug up to get to raw materials. This photo from Germany shows how brown coal mining strips away the topsoil. Through resource extraction, land that could provide wildlife habitat, or be used for agriculture or human habitation, is lost.

It takes 2,000 years for nature to produce a 10-centimeter (4-inch) layer of fertile soil that holds water and nutrients, and where plants can grow. To protect fertile soils worldwide, the United Nations has declared 2015 International Year of Soils.

In 1970, 3.7 billion people lived on the planet. Our numbers today exceed 7.5 billion. China and India top the global population list, with 1.4 billion and 1.33 billion inhabitants respectively. (Source: Statista, Deutsche Stiftung Weltbevölkerung)

About 64 percent of the world's population were rural dwellers in 1970. That's changed drastically. In 2016, the proportion had dropped to 45 percent. (Source: WorldBank)

We are becoming city people instead. The number of us living in urban areas rose from 1.34 billion in 1970 to 4 billion in 2016. According to the latest estimates, the majority of us are living in urban areas even in less developed countries. (Source: WorldBank)

People love cars, right? But do you know how many there are today? The exact figure is hard to come by but estimations draw a relatively a clear picture. In 1970, 250 million cars were on the road worldwide. That number shot up to 1 billion in 2010 and will have skyrocketed to 2 billion by 2020. The figures include cars, all kinds of trucks as well as buses. (Source: Wikipedia)

In 1970, the first Boeing 747 began its passenger service, flying 324 passengers from New York to London. Those 324 people were among the 310 million passengers who flew that year. Around 3.7 billion people took to the skies 2016. (Source: Worldbank)

Do you ever think about oil? Well, there's still plenty in the ground and we should keep it there if we want to avoid catastrophic climate change. But we actually put a lot of effort into getting the black gold out instead. Crude oil production has nearly doubled from 48,000 barrels a day in 1970 to 92,000 barrels in 2016. (Source: Statista)

Whatever we do, we create carbon emissions. And - rather unsurprisingly - we create a lot. Back in 1970, the world's population exhaled about 14.4 billion tons of CO2. In 2015, we breathed out about 35 billion tons. (Source: Statista)

The Amazon is one of the most precious and impressive rainforests on Earth. It's described as the world's green lung because it sucks up so much carbon dioxide. But mankind uses lots of wood and the lung is shrinking. Its area fell from 4,100,000 square kilometers in 1970 to 3,300,000 square kilometers in 2016. In other words, 81 percent of 1970's forest cover still remains. (Source: Mongabay)