Wildlife pop­u­la­tions in rapid de­cline

The Prince George Citizen - - Science - TODD WHITCOMBE

“Few peo­ple have the chance to find them­selves on the cusp of a truly his­toric trans­for­ma­tion... On one hand, we have known for many years that we are driv­ing the planet to the brink. The as­ton­ish­ing de­cline in wildlife pop­u­la­tions shown by the lat­est Liv­ing Planet In­dex – a 60 per cent fall in just over 40 years – is a grim re­minder and per­haps the ul­ti­mate in­di­ca­tor of the pres­sure we ex­ert on the planet. On the other hand, science has never been clearer about the con­se­quence of our im­pact.”

These are the open­ing lines to the 2018 Liv­ing Planet re­port by the World Wildlife Fund. In­volv­ing 59 sci­en­tists from a va­ri­ety of dis­ci­plines around the world, it is a fairly bleak view of the world we live in.

On the other hand, a re­cent re­port in the Jour­nal of Mam­mal­ogy en­ti­tled “How many species of mam­mals are there?” makes the point that over 1,000 new species of mam­mals have been dis­cov­ered in the past decade. In 1993, the to­tal num­ber of mam­mal species was 4,631. By 2005, it had in­creased to 5,416 and by 2018, the num­ber was 6,495.

How can we rec­on­cile these two re­ports? Don’t they con­tra­dict?

The an­swer is no. One is dis­cussing the to­tal an­i­mal pop­u­la­tion – the to­tal mass of an­i­mals, if you like – while the other is an as­sess­ment on the num­ber of va­ri­eties. As sci­en­tists con­tinue to scour the globe, they are find­ing new species of an­i­mals all the time. This has been aided by the lat­est ad­vance­ments in ge­nomic re­search as we can now ex­am­ine DNA to make dis­tinc­tions.

But the ac­tual num­ber of mam­mals on the planet is on the de­cline if we ex­clude hu­mans and do­mes­ti­cated species. This is made ap­par­ent in a rather sober­ing pas­sage from Yu­val Noah Harari’s book Homo Deus, when dis­cussing the An­thro­pocene.

He points out there are 300 mil­lion tons of hu­mans and 700 mil­lion tons of do­mes­ti­cated an­i­mals com­pared to just 100 mil­lion tons of large wild an­i­mals (de­fined as weigh­ing more than two kilo­grams).

He goes on to say “Al­to­gether about 200,000 wild wolves still roam the Earth, but there are more than 400 mil­lion do­mes­ti­cated dogs. The world con­tains 40,000 lions com­pared to 600 mil­lion house cats; 900,000 African buf­falo ver­sus 1.5 bil­lion do­mes­ti­cated cows; 50 mil­lion pen­guins and 20 bil­lion chick­ens. Since 1970, de­spite grow­ing eco­log­i­cal aware­ness, wildlife pop­u­la­tions have halved…”

He points out that at the be­gin­ning of the in­dus­trial rev­o­lu­tion, the num­bers were much dif­fer­ent with hu­mans and their do­mes­ti­cated species mak­ing up only 10 per cent of the large an­i­mal biomass on Earth. In­deed, in an­cient times, lions in­hab­ited south­ern Europe and mil­lions of bi­son roamed the plains of North Amer­ica.

Where does this leave us?

There have been five mass ex­tinc­tions on Earth where more than 75 per cent of the species alive have dis­ap­peared from the fos­sil record over rel­a­tively short pe­ri­ods of time.

Some de­clines, such as the Cre­ta­ceous Pa­le­o­gene ex­tinc­tion event 66 mil­lion years ago, ap­pear to be al­most in­stan­ta­neous in the fos­sil record.

Oth­ers have oc­curred over the space of 10,000 years. But in each case, there was a loss of both the to­tal num­ber of an­i­mals – the biomass – and the di­ver­sity of species.

We are not quite there yet in species loss but we are cer­tainly well on our way to a mass ex­tinc­tion with re­spect to biomass. And it is not just mam­malian crea­tures.

For ex­am­ple, wildlife pop­u­la­tions in rivers and lakes have fallen 83 per cent. Cen­tral and South Amer­ica have seen an 89 per cent drop in ver­te­brate pop­u­la­tions. And 50 per cent of plants have been de­stroyed since the be­gin­ning of civ­i­liza­tion.

For the sci­en­tists in­volved, the facts speak for them­selves and are a clear call for ac­tion.

In­deed, the Liv­ing Planet re­port as­serts we are the last gen­er­a­tion able to save the planet and calls for a Con­ven­tion on Bi­o­log­i­cal Di­ver­sity.

But when I look out­side, I see forests and plants. I have deer walk­ing down my road at night and rab­bits hop­ping around in the morn­ing. It is hard to see the global ef­fects when look­ing at a small scale and, for most of us, the small scale is the most ap­par­ent.

Yet it is the en­tire ecosys­tem which sus­tains life on this planet. The oceans pro­vide oxy­gen. The an­i­mals pro­vide bio­di­ver­sity.

The whole sys­tem is a com­plex equi­lib­rium and the one thing chemists know for sure about equi­lib­ria is that al­ter­ing them changes the set point. In this case, not for the bet­ter.

To quote Harari again: “Homo Sapi­ens have rewrit­ten the rules of the game. This sin­gle ape species has man­aged within 70,000 years to change the global ecosys­tem in rad­i­cal and un­prece­dented ways... our im­pact may sur­pass that of the as­teroid that killed off the di­nosaurs 65 mil­lion years ago.”

What does the fu­ture look like? The choice is ours.


An African buf­falo stares at vis­i­tors to cen­tral Kenya’s Meru Na­tional Park in 2005. While African buf­falo re­main fairly nu­mer­ous – ap­prox­i­mately 900,000 an­i­mals in the wild – their pop­u­la­tion is dwarfed by the num­ber of do­mes­tic cows, es­ti­mated at 1.5 bil­lion. Hu­mans and our do­mes­ti­cated an­i­mals out­weigh the pop­u­la­tion of large wild an­i­mals (two kilo­grams and larger) by 10 to one.

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