A pine marten in a Highland garden made me ponder the sixth mass extinction

While on holiday in the Highlands last week, I was treated to a sight I thought I would never see.

On a still evening I noticed a rustling in the branches of a cherry tree in the garden of the house where we were staying. I saw a furry tail and at first thought it must be a cat, but it moved differently, more like a weasel or a ferret, only it was too big to be one of them.

Then it turned towards us, revealing the giveaway rusty coloured neck and chest of a pine marten.

Judging by its size, we guessed it was a male and our children named him Jimmy.

Jimmy returned to the same tree the next evening, gorging on the cherries on the branches and hoovering up others that had fallen to the ground.

As a boy, in the 1980s and 90s, I became resigned to the notion that, like so many of our native species, I would probably never see a pine marten in the wild. Their numbers were perilously low and seemed to be heading in only one direction.

Obviously, Jimmy’s existence needn’t mean the species was any less imperilled - perhaps he was the only one in a 50-mile radius - so I looked into how they were doing.

And it turns out pine martens are doing far better than I had thought. 

According to Nature Scotland, the species, which was given full legal protection in 1988, is recovering but “still rare”, with a Scottish population of around 3,700 adults. Their territories are expanding and new colonies are becoming established across Britain.

In my childhood I was pessimistic about ever seeing any species of whale in the wild. Now I am optimistic, as there are frequent sightings off the British coastline.

Populations of species such as the blue, sperm, bowhead, right and minke whale are steadily rising. In the 1960s, the world population of humpback whales was thought to be just 5,000, compared with 135,000 today.

As we headed home from holiday, we stopped off at the Highland Wildlife Park near Aviemore to see, amongst other animals, the polar bears.

Like the whale, the polar bear was once a poster child for the environmentalist movement but it turns out they are faring far better than might be expected.

When scientists began studying polar bear populations in the 1960s it was feared there could be as few as 5,000 left in the wild. 

Since then, there has been a concerted drive to regulate or ban hunting, and the latest estimate of the Polar Bear Specialist Group of the International Union for the Conservation of Nature and Natural Resources puts the number of polar bears in the wild at 26,000.

Tigers also prowl the park in the Cairngorms, as they do at Edinburgh Zoo, where a noticeboard on population numbers makes grim reading.

It says that in 1900, 100,000 tigers roamed across Asia, but that today there are fewer than 4,000. The Bali, Caspian and Javan tigers were declared extinct in, respectively, the 1940s, the 1970s and the 1980s.

But, thankfully, numbers are now rising and the zoo’s noticeboard is out of date. According to the Global Tiger Forum, numbers hit an all-time low of 3,200 in 2010. Last year, the forum estimated the world wild tiger population to be around 5,574 - a 74 per cent increase in 13 years.

The welcome recoveries that we have seen in recent years in populations of pine martens, whales, polar bears and tigers have a common thread that has nothing to do with fossil fuels or carbon dioxide. It is simply that we have, by and large, stopped killing them.

Wolves are another success story, rapidly recolonising former territory in much of Europe and North America. 

But there are causes for alarm, with species such as lions and African elephants continuing to decline.

Why might it be that wolves are increasing in number in rich European and North American countries, while lions are decreasing in poor African countries? 

Human prosperity is arguably the best hope for threatened species. If people can stop being dependent upon or in competition with wildlife they begin caring for it instead. 

People who are forced to scratch around wondering where their next meal is going to come from will understandably prioritise sustaining themselves over their environment. 

If some African communities were more prosperous there would be less temptation to risk killing elephants to sell their ivory. Perhaps they would instead protect the elephants to boost tourism.

And given access to efficient fuel, they might clear less forest to use for cooking.

Fortunately for biodiversity, the world as a whole is now reforesting rather than deforesting, particularly in wealthier countries, according to a satellite analysis by scientists at the University of Maryland.

And the slight increase in recent decades in carbon dioxide from the dangerously low level of less than 0.03 per cent of the air to more than 0.04 per cent now means the Earth is, literally, getting greener. 

The global greening is particularly pronounced in arid areas previously lacking vegetation such as Western Australia and the African Sahel. 

Again, good news for biodiversity, perhaps not so good for populations of scorpions and such like that might want to gravitate closer to the Equator.

Yes of course there are problems, with pollution, overfishing and invasive species causing unique subspecies to go extinct.

But I struggle to believe that we are, as many environmentalists claim, in the midst of the Earth’s “sixth mass extinction” (the fifth one being the fallout of the asteroid impact that wiped out the dinosaurs 66 million years ago).

On the contrary, the evidence of recent decades seems to give grounds for hope that, through human prosperity, education and conservation, more species can be brought back from the brink.