President Vladimir Putin has put Russia's nuclear forces on high alert. The theory is that the possibility of mutually assured destruction is the strongest of reasons not to press the button. But the pressure is mounting.

Strict water restrictions come into force for millions of people in California as the US west coast continues to experience a crippling drought.

People are increasingly interested in seeing animals in natural settings, so traditional jail-like zoos are giving way to open-plan zoos, and to eco-tourism.

Barbary macaques are among the most popular tourist attractions in Gibraltar. The apes have a taste for junk food, which enables tourists to see them up close and allows scientists to easily capture them for research.

We leave the macaques in Gibraltar to travel to the Galapagos Islands to learn about marine and land iguanas.

The segment focuses on the alien striped iguanas of the Galapagos Islands, albinism in a variety of animals, and the peppered moth.

The last segment focuses on Australia. We visit the Warrawong Earth Sanctuary, where there are breeding programs to reintroduce such indigenous animals as bandicoots and quolls, creatures that came close to extinction.

In the next 35 years, we’ll have to produce more food than all of the world’s production over the last 2000 years combined. So what will the farms of the future look like?

Prime Minister David Cameron will step down by October after the UK voted to leave the European Union. Mr. Cameron made the announcement in a statement outside Downing Street, in which he said he will attempt to "steady the ship" over the coming weeks and months, but that "fresh leadership" is needed.

"Brexit" is a portmanteau that blends "Britain" and "exit", and refers to Britain leaving the European Union. The decision was made by referendum, in which a narrow majority of British voters chose to leave the European Union. This video (part 1 of 3) succinctly outlines the plans that Britain's Prime Minister and the Members of Parliament are grappling with on the eve of Britain's exit from the European Union on March 29, 2019.

This segment outlines the advantages and the drawbacks for British businesses in different versions of Brexit. The rights of British citizens living in EU countries and EU citizens living in Britain are also discussed.

The focus of this segment is on the Chequers Deal, the preferred deal of Prime Minister Theresa May, which blends aspects of both Hard and Soft Brexit deals. It also outlines what could happen if no deal is struck by the deadline.

How do you transport life-saving medicines that need to be kept cold to remote communities, even across deserts or through dense jungles? Find out more about the cold chain process.

The city of Oxford is home to some 150,000 residents and a famous seat of learning, the oldest English-speaking university in the world. Although the exact date of its founding isn't known, it is said that local priests and monks were first taught in monastery schools in the area in the eleventh century.

Happy New Year to everybody on our beautiful planet Earth from the International Space Station!