This is John Bachelor, continuing my conversation with Professor Peter Frankopan, historian as well as the author of the new book,

The Earth Transformed, an Untold's History, which is a history that reveals how climate change shapes the development and demise

of civilizations over the last 4,000 years. However, we have an immediate challenge and the professor describes what may be ahead of us in Pakistan in parts of the world

where the water supply depends upon the glaciers of the Himalayas that are apparently in retreat.

The professor here describes what that would lead to, what that is leading to,

he's just returned from Pakistan, having looked at the problem

of salinity, and what that means for food production and anticipation of disaster ahead.

Professor Peter Franklin, the book is The Earth transformed.

Much more of this tonight.

Thank you.

Well, all of those investments were primarily around making the movement of goods and people cheaper, more efficient.

So they weren't, they weren't done to, you know, as acts of charity, they had a specific role in the administration of the Indian subcontinent and in being able to make it more efficient

and its goods more available at lower prices. So in that sense, undoubtedly, the things that were more complicated and went more badly wrong were building of dams across

rivers in ways that were thought to be able to show the mastery of man over nature that then

cut off water supplies for people downstream.

All the creation of colonies in the called worker colonies in the Punjab,

the border that was now split between India and Pakistan, where millions of people were encouraged to settle in land that was going to be newly irrigated.

That proved very unsuccessful because when you have new canals that deliver water to fields in very high temperatures, the water evaporates quickly and can make the soil saline.

And when you have high levels of

evaporation and salinity, those soils can be killed for forever.

And so the yields were very high on the in the Punjab

in particular, the bread basket of the Indian subcontinent, but over the course of four or five decades,

...