Which desert covers much of Mongolia and northern China?

The Gobi, and it is a cold desert - temperatures swing from around 40 degrees in summer to minus 40 in winter, and it snows. It is a rain shadow desert, dry because the Himalayas block the monsoon from reaching it rather than because it is hot.

It is the best dinosaur locality on Earth. The 1920s American expeditions there found the first dinosaur eggs anyone had recognised, and the fossils since have included the Fighting Dinosaurs - a Velociraptor and a Protoceratops preserved mid-combat, buried by a collapsing dune with the raptor's claw at the other animal's throat. Fossils there are often found weathering out of bare rock with no digging required.

It is also expanding, by thousands of square kilometres a year, driven by overgrazing, deforestation and drought - and the dust storms reach Beijing, Korea and occasionally North America. China's response has been the Three-North Shelterbelt, a programme of tree planting running since 1978 and intended to continue to 2050, sometimes called the Great Green Wall. Its effectiveness is disputed: survival rates for the trees have been poor in places, and planting thirsty species in dry ground can lower the water table further.