This week's programme is ostensibly about Komodo dragons
, but Stephen and I started our travels in Malaysian Borneo - and that's where we experienced our personal highs and lows of the trip.
We had an amazing few days filming at a blissful tropical island called Sipadan, which is one of the best dive sites in the world
. As Stephen put it at the time: "You know the saying, 'The grass is always greener on the other side of the fence?'. Well, this is the other side of the fence."
But there is one sight in Borneo that neither of us can get out of our minds: the palm trees. Vast swathes of what was once tropical rainforest have been cleared to make way for row upon row, mile upon mile of identical palms.
It is such a huge problem that the rapid expanse of palm oil plantations in Southeast Asia could be the single most immediate threat to the greatest number of species on the planet. When the forest goes, so does most of the wildlife - indeed, palm oil is now considered the biggest threat to orangutans.
Palm oil is a key ingredient of many processed foods (though it's usually listed simply as 'vegetable oil') and is in huge demand as a source of non-hydrogenated fats. It is also used to produce biofuel, even though clearing the forests releases so much carbon dioxide into the atmosphere that the damage caused outweighs the benefits of switching to a so-called environmentally-friendly fuel.
Malaysia and Indonesia are by far the largest exporters of palm oil. Their economies rely on it - and so do the livelihoods of millions of people. In fact, the incentives to produce palm oil are so great that national park and reserve boundaries are often changed to make way for new plantations.
There are solutions. For a start, there is plenty of non-forested land that would be perfectly good enough to meet the growing demand for palm oil plantations. But even so, the greedy corporations prefer to bulldoze the rainforests to make extra money out of their valuable timber.
If you'd like to find out more about palm oil and what's being done to tackle the problem have a look at the following websites;