We live in a zoologically impoverished world…
So said Alfred Wallace, co-discoverer of the process of natural selection.
But just how zoologically impoverished is our world?
Unless you’re living in certain areas of Africa, a quick look around your local patch will find that it’s rather shy of megafauna. Across time, human over-hunting and cascading co-extinctions have put to bed a startling array of our largest co-inhabitors.
From the giant ground sloths of the Pampas, to the elephant birds of Madagascar and the Steller’s sea cow of the Commander islands (not to mention the aurochs, bears, wolves and lynxes that would once have roamed the UK), we’ve been systematically downsizing Earths fauna for some time now.
Human-driven extinctions and degradation of ecosystems are by no means a new phenomena. What is rather new, though, is the meticulous, global measurements of what we are doing to Earth and its species. That’s why most headlines you might read around the unfurling of wild nature talk about the impacts of humanity over the last forty years or so.
That’s around the time we have good quality population estimates of many species, and so we can start to track the magnitude of human impacts. A few decades after that is also when we have access to the sort of satellite imagery that shows us how ecosystems are being altered and changed by humans through time.
Stretching back later than the late 20th century, however, things start to get a whole lot patchier.
There are plenty of signals and clues that the world is not quite how it once was, and that we have been exerting our planetary influence for far longer than most of us might first suspect—for many, many thousands of years in some cases. Just looking at the world’s three biggest chunks of rainforest, there is a pretty clear fingerprint of extended human disturbance visible in the palaecological and archaelogical records of the Amazon and Congo Basins, as well as in the Indo-Malayan region of Southeast Asia.
But the sort of high quality data on the makeup of ecosystems and the abundance of species are especially revealing when considering biodiversity trends go almost silent much past the 1960s.
That’s why the few rare examples of scientists tracking long-term changes in ecosystems and species trends are so interesting and important. They grab us by the earlobes and tug us back in time, reminding us of how things once were. They help refocus our ever-shifting baselines, and reposition the yardstick by which we judge today’s enviroments.
Here are some of my favourite pieces of science that have done just that:
Retrawling like the old-school
How do you find out how fish assemblages have changed over a century on an inshore bank off South Africa? Well, one way is to get funky with some Manila rope and fibre-core cable and reconstruct the trawling gear of old used by fisherman in times gone by. Then, simply head back to the same sites and carry out some historically-renacted retrawls… This study did just that to track how over a century of trawling has reconstructed the sea floor and the communities of animals living on it.
Cold War marmots
And what about when you want to see how populations of barbok marmots have fared in the grasslands of Kazakstan? In this case, you make use of the fact that barbok marmots create burrows that they return to across generations. Using satellite images taken from up on high , you can count the number of burrows across the decades and get an idea of how many dastardly barbok marmots are knocking around.
Just one problem. Satellite images taken at high enough resolution that you can make out a few holes gouged into the ground aren’t all that common in the early ’60s. Fortunately, in this case, spy planes launched by the United States to peek on Soviet missile sites around then are just the sort of holiday snaps needed to do some barbok science.
Using these images, scientists recently showed how barbok burrow numbers have dropped by 14% since the ’60s, with the number of burrows in some of the oldest agricultural fields plummetting by 60%.
The orangutan diaries
Surely one of the most exciting revelations of the past few decades was the identification of an entirely new species of Great Ape, the Tapanuli organutan–a species formally described in 2017. The species numbers only 800 individuals and is split across three subpopulations in the Sumatran highlands, occupying only a tiny 1000km2 area of upland forest.
Trawling through Dutch and German colonial literature, newspapers, journals, books and museum records from the early 1800s to 2009, scientists recently used the lens of written history to change what we know about this magnificent, range-restricted orang. It turns out that by converting written records of this orangutan into a maps of occurence, we can see that the Tapunuli orangutan once lived across a much wider range of habitat types and at lower elevations than it does today. In fact, the species only occurs in about 2.5% of its 1890s historical range! A stark reminder that the lens of today is almost always a poor indicator of naturalness.
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