Five of the world's biggest environmental problems

These five megatrends present major global threats for planet Earth — problems that must be solved if the world is to remain a supportive habitat for humans and other species. DW looks at causes and possible solutions.

1. Air pollution and climate change.

Problem: Overloading of the atmosphere and of ocean waters with carbon. Atmospheric CO2 absorbs and re-emits infrared-wavelength radiation, leading to warmer air, soils, and ocean surface waters - which is good: The planet would be frozen solid without this.

Nature and Environment | 11.10.2016

Unfortunately, there's now too much carbon in the air. Burning of fossil fuels, deforestation for agriculture, and industrial activities have pushed up atmospheric CO2 concentrations from 280 parts per million (ppm) 200 years ago, to about 400 ppm today. That's an unprecedented rise, in both size and speed. The result: climate disruption.

Carbon overloading is only one form of air pollution caused by burning coal, oil, gas and wood. The World Health Organization recently estimated that one in nine deaths in 2012 were attributable to diseases caused by carcinogens and other poisons in polluted air.

Solutions: Replace fossil fuels with renewable energy. Reforestation. Reduce emissions from agriculture. Change industrial processes.

Nature and Environment | 02.08.2017

The good news is that clean energy is abundant - it just needs to be harvested. Many say a 100 percent renewable-energy future is feasible with existing technology now.

But the bad news is that even though renewable energy infrastructure - solar panels, wind turbines, energy storage and distribution systems - are already widespread, and getting cheaper and more efficient all the time, experts say we're not applying them quickly enough to prevent catastrophic climate disruption. Barriers in policy and finance remain to be overcome.

Picture gallery: The big smog: Cities plagued by air pollution

The big smog: Cities plagued by air pollution

Ulan Bator, Mongolia

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 big smog: Cities plagued by air pollution

Beijing, China

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.

The big smog: Cities plagued by air pollution

Lahore, Pakistan

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.

The big smog: Cities plagued by air pollution

New Delhi, India

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.

The big smog: Cities plagued by air pollution

Riyadh, Saudi Arabia

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 big smog: Cities plagued by air pollution

Cairo, Egypt

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.

The big smog: Cities plagued by air pollution

Dhaka, Bangladesh

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.

The big smog: Cities plagued by air pollution

Moscow, Russia

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 big smog: Cities plagued by air pollution

Mexico City, Mexico

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.

2. Deforestation.

Problem: Species-rich wild forests are being destroyed, especially in the tropics, often to make way for cattle ranching, soybean or palm oil plantations, or other agricultural monocultures.

Today, about 30 percent of the planet's land area is covered by forests - which is about half as much as before agriculture got started around 11,000 years ago. About 7.3 million hectares (18 million acres) of forest are destroyed each year, mostly in the tropics. Tropical forests used to cover about 15 percent of the planet's land area; they're now down to 6 or 7 percent. Much of this remainder has been degraded by  logging or burning.

Not only do natural forests act as biodiversity reserves, they are also carbon sinks, keeping carbon out of the atmosphere and oceans.

Solutions: Conserve of what's left of natural forests, and restore degraded areas by replanting with native tree species. This requires strong governance - but many tropical countries are still developing, with increasing populations, uneven rule-of-law, and widespread cronyism and bribery when it comes to allocating land use.

Picture gallery: Burning down the Amazon

Burning down the Amazon

Scorched earth

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.

Burning down the Amazon

Trading wood for wheat

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.

Burning down the Amazon

Dams for the cities

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.

Burning down the Amazon

Good business?

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.

Burning down the Amazon

Fines for felling trees

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.

Burning down the Amazon

Where trees are products

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.

Burning down the Amazon

Swath of destruction

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.

Burning down the Amazon

The Crocodile Bar

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.

Burning down the Amazon

Fleeing the gold-diggers

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.

Burning down the Amazon

Origin of barbecue charcoal

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.

3. Species extinction.

Problem: On land, wild animals are being hunted to extinction for bushmeat, ivory, or "medicinal" products. At sea, huge industrial fishing boats equipped with bottom-trawling or purse-seine nets clean out entire fish populations. The loss and destruction of habitat are also major factors contributing to a wave of extinction - unprecedented in that it is caused by a single species: humans. The IUCN's Red List of threatened and endangered species continues to grow.

Not only do species inherently deserve to exist, they also provide products and "services" essential to human survival. Think bees and their pollinating prowess - necessary for growing food.

Solutions: Concerted efforts need to be made to prevent further loss of biodiversity. Protecting and restoring habitats is one side of this - protecting against poaching and wildlife trade is another. This should be done in partnership with locals, so that wildlife conservation is in their social and economic interest.

Picture gallery: Looming extinction crisis 

Looming extinction crisis

100 times faster

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.

Looming extinction crisis

In the red

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.

Looming extinction crisis

Pollution, deforestation, climate change

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.

Looming extinction crisis

'Sixth mass extinction event'

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.

Looming extinction crisis

Fossils as reference

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.

Looming extinction crisis

Threatened ecosystems

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.

Looming extinction crisis

Humankind at risk

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.

Looming extinction crisis

Need for accelerated action

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.

4. Soil degradation.

Problem: Overgrazing, monoculture planting, erosion, soil compaction, overexposure to pollutants, land-use conversion - there's a long list of ways that soils are being damaged. About 12 million hectares of farmland a year get seriously degraded, according to UN estimates.

Solutions: A wide range of soil conservation and restoration techniques exist, from no-till agriculture to crop rotation to water-retention through terrace-building. Given that food security depends on keeping soils in good condition, we're likely master this challenge in the long run. Whether this will be done in a way equitable to all people around the globe, remains an open question.

Picture gallery: When the earth turns to dust 

When the earth turns to dust

Going underground

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.

When the earth turns to dust

Sealed over

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.

When the earth turns to dust

Creeping erosion

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.

When the earth turns to dust

Ongoing desertification

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.

When the earth turns to dust

Exhausted land

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.

When the earth turns to dust

Widespread contamination

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.

When the earth turns to dust

Resource extraction

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.

When the earth turns to dust

New life

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.

5. Overpopulation.

Problem: Human population continues to grow rapidly worldwide. Humanity entered the 20th century with 1.6 billion people; right now, we're about 7.5 billion. Estimates put us at nearly 10 billion by 2050. Growing global populations, combined with growing affluence, is putting ever greater pressure on essential natural resources, like water. Most of the growth is happening on the African continent, and in southern and eastern Asia.

Solutions: Experience has shown that when women are empowered to control their own reproduction, and gain access to education and basic social services, the average number of births per woman drops precipitously.

Done right, networked aid systems could bring women out of extreme poverty, even in countries where state-level governance remains abysmal.

Picture gallery: Remember when we used just one earth?

Remember when we used just one earth?

Many more of us

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)

Remember when we used just one earth?

Where do you live?

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)

Remember when we used just one earth?


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)

Remember when we used just one earth?

What's your ride?

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)

Remember when we used just one earth?

Like taking a bus

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)

Remember when we used just one earth?

Keep it in the ground?

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)

Remember when we used just one earth?

Up in the air

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)

Remember when we used just one earth?

What about the green lung?

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)

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