With modern technology and firepower it takes little courage and even less skill to kill wild animals. This week James Palmer, a US dentist and recreational “big-game hunter”, found himself in the crosshairs as an international controversy exploded over his casual slaughter of an iconic Zimbabwean lion known as Cecil.

Palmer had paid $50,000 (€45,000) for the privilege of killing a lion for sport, an activity that is technically legal in Zimbabwe. Cecil was based in the protected Hwange National Park; lured out with bait, he was then inexpertly shot by Palmer with a crossbow.

The semi-tame lion, which had been fitted with a GPS tracking device as part of a long-term Oxford University study, fled, wounded, and survived for 40 agonising hours as the weekend warrior and his guides stalked it across the savannah.

Palmer’s online profile boasts of at least 43 other “kills” of wild and endangered animals, from polar bears to leopards and buffalo. However you may feel about the Minnesota dentist’s idea of fun, what makes his case unusual is that, for once, the world took notice.

Cecil’s fate has been similar to that of countless billions of other living creatures in recent decades. The World Wide Fund for Nature’s 2014 Living Planet Index confirmed the depth and severity of the global biodiversity crux: habitat loss and degradation, pollution and climate change have led to a precipitous decline of 52 per cent in the number of mammals, birds, reptiles, amphibians and fish.

Put another way, for every two wild creatures alive on Earth in 1970, only one remains today.

“This global trend suggests we are degrading natural ecosystems at a rate unprecedented in human history,” according to the World Wide Fund for Nature. Species extinctions are difficult to quantify, but scientists estimate that 50,000 species are disappearing every year – that’s 135 species a day, every day. This is at least 1,000 times higher than the “background”, or natural, extinction rate.

It is no coincidence that in just the four decades since 1970, as the natural world has undergone unprecedented decline, human numbers have doubled, to more than seven billion, and the global economy has more than quadupled.

The global economy is eating the foundations of life on Earth by consuming its natural capital at a rate far in excess of the planet’s ability to regenerate, and by accumulating the toxic byproducts of global industrial and agricultural activity so rapidly it is overwhelming the capacity of the biosphere to absorb those products and render them harmless.

In just the past 15 years the hunger for resources has seen the world’s rainforests being felled at the astonishing rate of the equivalent of 50 football pitches every minute. On an annual basis that’s an area of rich biodiversity twice the size of Ireland lost forever. Our own record isn’t much better. Ireland’s ecologically rich peatlands are being progressively destroyed by a combination of Bord na Mona and private contractors using heavy industrial equipment.

Given our careless collective evisceration of the natural world, why have millions of people been so moved by the fate of a single lion?

Dr Ernest Small, a biodiversity specialist, has researched why humans seem to favour some animals over others. (The World Wide Fund for Nature, for example, has the cuddly panda as its logo.) He writes, “Most humans are not just ignorant of but indifferent to almost all of the species on the planet . . . and are slightly to extremely negative towards the majority of species they encounter.”

The exception to this rule is our collective attitude towards what are known as charismatic megafauna – large, photogenic animals, notably elephants, giraffe, big cats and bears. “You can’t get much more charismatic than a lion. Here we are as humans getting very excited about charismatic animals. We never think about all the pain we cause to billions of sentient creatures,” Small told ThinkProgress.org.

Apex predators such as big cats, wolves and sharks play pivotal roles in their ecosystems. Trophic cascade – the top-down regulation of ecosystems by predators – is an essential element of an intact ecosystem. Targeting top predators has negative consequences far beyond just one species.

Fifty years ago Africa had 500,000 lions in the wild. Today that number is down by more than 95 per cent, to barely 20,000. More tigers are kept as "pets" in the US today than remain in the wild worldwide. Meanwhile, in Africa this week, Barack Obama promised a crackdown on the ivory trade that is leading to the grisly slaughter of 25,000 elephants a year.

Barring a profound change of attitude, we are on track to be the last generation to share Earth with these magnificent wild animals. Their destruction at our hands would be an indelible stain on our species – and a spectacular evolutionary own goal for Homo sapiens.

John Gibbons is an environmental writer; @think_or_swim