Quiz of the Day
Environment & Planet
Friday, 5 June 2026
World Environment Day — ecosystems, climate action, nature records
1. World Environment Day has been celebrated every 5 June since which year?
- 1974
- 1992
- 1985
- 1960
The day was established by the UN General Assembly in 1972 but first held in 1974 with the slogan 'Only One Earth.' Each year a different country hosts the event — it is the UN's largest annual platform for environmental outreach, engaging millions worldwide.
2. What percentage of Earth's surface is covered by oceans?
- About 71%
- About 80%
- About 50%
- About 61%
Despite covering 71% of the surface, oceans hold 97% of all Earth's water. We have explored less than 20% of the ocean floor — meaning we know more about the surface of Mars than we do about our own ocean depths.
3. What is the Great Barrier Reef and where is it located?
- A rock formation in Africa
- A mountain range in South America
- The world's largest coral reef system, off Australia
- An ice shelf in Antarctica
The Great Barrier Reef stretches over 2,300 km and is visible from space. It is actually made up of nearly 3,000 individual reef systems and supports over 1,500 species of fish. It has lost over half its coral since 1995 due to bleaching events.
4. Which gas makes up the largest proportion of greenhouse gas emissions from human activity?
- Ozone
- Methane
- Nitrous oxide
- Carbon dioxide
CO2 accounts for about 75% of global greenhouse emissions. A single return flight from London to New York produces roughly 1 tonne of CO2 per passenger — about the same as the average person in some countries emits in an entire year.
5. What is biodiversity?
- A type of renewable energy
- The variety of all living things on Earth
- The study of biology
- The classification of species
Scientists estimate there are 8.7 million species on Earth, but about 86% of land species and 91% of marine species have not yet been described. We are losing species at 1,000 times the natural background rate — a pace not seen since the dinosaurs vanished.
6. The Amazon Rainforest produces roughly what percentage of the world's oxygen?
- About 6%
- About 20%
- About 30%
- About 15%
The popular claim that the Amazon produces 20% of Earth's oxygen is actually a myth. It produces about 6%, but it consumes nearly as much through decomposition. Its real superpower is absorbing 2 billion tonnes of CO2 per year — acting as a massive carbon sink.
7. What is the Paris Agreement's main goal?
- To ban all fossil fuels by 2030
- To plant 1 trillion trees
- To limit global warming to well below 2 degrees C above pre-industrial levels
- To make all countries carbon neutral by 2025
Signed by 196 parties in 2015, the agreement also pursues efforts to limit warming to 1.5 degrees C. Even half a degree makes an enormous difference: at 2 degrees C, virtually all coral reefs die; at 1.5 degrees C, 10-30% may survive.
8. Which country has the most forests by total area?
- Russia
- Canada
- Brazil
- United States
Russia has about 815 million hectares of forest — over 20% of the world's total. However, Siberian forests are increasingly threatened by wildfires. In 2021, Russia's forest fires burned an area larger than all other countries' fires combined.
9. What is the 'ozone layer' and why is it important?
- A layer of oxygen at sea level that helps us breathe
- A band of pollution around cities
- A type of greenhouse gas barrier
- A layer in the stratosphere that absorbs most of the Sun's harmful UV radiation
The 1987 Montreal Protocol banned CFCs that were destroying the ozone layer. It is considered the most successful environmental treaty ever — the ozone hole is expected to fully recover by about 2066. It proves global cooperation on environmental issues can work.
10. Approximately how many trees are cut down worldwide each year?
- About 15 billion
- About 3 billion
- About 25 billion
- About 7 billion
Humans cut down about 15 billion trees per year, while only about 5 billion are replanted. Since the start of human civilisation, the total number of trees on Earth has fallen by roughly 46%. There are currently about 3 trillion trees left — roughly 400 per person.
11. What is 'rewilding'?
- Banning all hunting
- Releasing zoo animals into the wild
- Planting only native species
- Restoring natural processes and ecosystems by reducing human control
One of the most famous rewilding examples is the reintroduction of wolves to Yellowstone in 1995. The wolves changed elk behaviour, which allowed vegetation to recover along rivers, which stabilised riverbanks — the wolves literally changed the course of rivers.
12. Which single-use item is the most commonly found piece of ocean litter?
- Food wrappers
- Plastic bottles
- Cigarette butts
- Plastic bags
Over 4.5 trillion cigarette butts are discarded globally each year, making them the world's most littered item. The filters are made of cellulose acetate, a type of plastic, and can take up to 10 years to decompose while leaching toxic chemicals.
13. What was the 'Dust Bowl' of the 1930s?
- A sandstorm in the Sahara
- A period of devastating dust storms in the American Great Plains caused by poor farming practices
- A severe drought in Australia
- A volcanic eruption in Mexico
Over-ploughing had stripped native grasses. When drought hit, topsoil blew away in 'black blizzards' that reached New York and Washington DC. About 2.5 million people fled the region. It led to the creation of the US Soil Conservation Service and modern soil management.
14. Which renewable energy source generates the most electricity globally?
- Geothermal
- Hydropower
- Solar
- Wind
Hydropower generates about 16% of the world's electricity and around 60% of all renewable electricity. China's Three Gorges Dam is the world's largest power station by capacity, generating 22,500 MW — enough to power about 15 million homes.
15. What is the term for the mass extinction event currently being driven by human activity?
- The Anthropocene Collapse
- The Great Dying
- The Human Impact Event
- The Sixth Mass Extinction
Earth has experienced five mass extinctions before — the worst killed 96% of all species 252 million years ago. Current extinction rates are 100 to 1,000 times higher than natural background rates. Since 1970, wildlife populations have declined by an average of 69%.