Are Humans Increasing the Number of Species?

After decades of researching the impact that humans are having on animal and plant species around the world, Chris Thomas has a simple message: Cheer up. Yes, we’ve wiped out woolly mammoths and ground sloths, and are finishing off black rhinos and Siberian tigers, but the doom is not all gloom. Myriad species, thanks in large part to humans who inadvertently transport them around the world, have blossomed in new regions, mated with like species and formed new hybrids that have themselves gone forth and prospered. We’re talking mammals, birds, trees, insects, microbes—all your flora and fauna. “Virtually all countries and islands in the world have experienced substantial increases in the numbers of species that can be found in and on them,” writes Thomas in his new book, Inheritors of the Earth: How Nature Is Thriving in an Age of Extinction.

That is the introduction to a very interesting interview with Chris Thomas, a conservation biologist. Read the whole thing.

Hat tip: The Browser.


Over the Hedge (2006 movie) had some truth to it. There are a heck of a lot more red tree squirrels in the Orange County sprawl than there were 30 years ago. Like from zero to a million. And the little buggers like to bite all the avocados on a tree. Their way of looking for ripe ones.

I suppose in time this could balance out to integrated environments, but there are short term damages - lakes clogged by a new weed or mussel, etc

Or we're just discovering species which we hadn't got to yet. Doesn't have to mean they're newly created in the last few years.

why is alex tabarrok posting a tyler post?

@AlexTaborrok: "Cheer up"

Who is it that needs cheering-up on this trivial issue?

Well, the Center for Biological Diversity for one. "THE EXTINCTION CRISIS It's frightening but true: Our planet is now in the midst of its sixth mass extinction ..."

I have another story. I was hiking last week in the Santa Monica mountains. As I came back down the trail a midsized coyote was coming up. I told it to stop. It did. It waited as they do. I shouted at it to go away. So it turns around and starts trotting down the trail. I follow. A little bit latter a runner comes up the trail. Runner and coyote calmly pass each other. Then the runner does a big double take and says "was that a coyote? I thought that was your dog!" This continues down the trail, past other hikers and dogs on leashes. The last hiker I see before the road says "is he with you?" So I reach the road, and "my" coyote runs up a little hill, turns around and grins at me. I continue on.

I guess this coyote has us figured out as not dangerous, and possibly bearing small dogs.

The coyotes population in NY has exploded. Eastern coyotes tend to be significantly larger (possible wolf hybrids). Is the California coyote growing larger? Over the past two years, two of my younger, hunting buddies each killed a coyote while (northern Catskills) NY deer hunting.

The white-tail deer population is now much higher than 150 years ago. They are serious problems (cars, shrubbery, and Lyme's disease) in eastern Long Island. Now they are being sighted in Nassau County. The first Bentley that gets dented will spell their doom.

Have you seen a mountain lion in your hiking? Lions frighten me, even when I carry a high-powered rifle. They can stalk you. Old farts are far easier prey than deer. One of our hunt club members (former USAF PJ) saw a big cat on one of our North Woods (in the Adirondacks) hunts.

I don't think we have hybrids here. I would guess that this coyote was a 2 year old. Very pretty tail with a white band and black tip.

I spend about half my time near those mountains. We were relayed news of a tv story of a mountain lion in a back yard, caught on security cameras. It turned out it was the next door neighbors. Our dog had been going nuts that night.

The main thing for us is that we can't let the dog out by herself at night.

All the coyotes in our area are nice and plump. None of the desperation needed to take on a 4-foot tall human I wouldn't think.

Shakespeare's Caesar gets it: "Yond Cassius has a lean and hungry look."

Mountain lions are scary in theory, but are a non-factor in reality. If they wanted to, they could massacre people in the woods because of their stealth. You're right to be skeptical of the value of your rifle, because you wouldn't even know the mountain lion was there, until its jaws closed around the back of your neck.

Fortunately, mountain lions almost never view humans as food and instead view us as beings to avoid. The evidence? Look at the number of fatal mountain lion attacks in North America over the centuries (e.g. wikipedia's list). It's a ridiculously small number -- less than a single death every two years -- despite the close proximity that humans often have to mountain lions.

The list of things that are more likely to kill you than a mountain lion is extremely long: Bees. Dogs. Lightning. Also fleas (plague has killed more people in recent years than mountain lions have) and ticks (Lyme disease and Rocky Mountain Spotted Fever have killed even more) -- and thus rodents too (Hanta virus, plus they carry fleas). Plus mosquitoes and birds (West Nile disease). And perhaps the deadliest risk: driving from your home to the great outdoors. Most of the people who die in national parks or forests are killed in traffic accidents. A few die because they get lost or caught in bad weather or fall off a cliff. The number who are killed by mountain lions is so small that you literally have a better chance of winning the lottery (if you play it repeatedly).

But those are the facts for adults. People who live in Los Angeles (where a mountain lion even decided to take residence in Griffith Park, which is somewhat akin to Prospect Park in Brooklyn in terms of being far from the urban periphery indeed somewhat close to the central city) know that cats and dogs are at risk from both mountain lions and coyotes. Children are also a good prey-size for a mountain lion. That doesn't mean that you have to wring your hands if your six-year old walks out of sight around the bend in the trail -- again the probabilities are overwhelmingly in your favor. But it's a good idea to keep an eye on them anyway, and cougars and coyotes are one of the reasons.

Here in San Francisco they have adapted to city living especially in the Presidio where we walk. With several dens it is not uncommon for a coyote to trot right on by as we hike. At first glance they do look like dogs. Very shy not at all threatening.

My impression is that certain intelligent, flexible, generalist species -- such as coyotes, crows, and black bears -- have done very well from the increasing human population of North America, while more specialist species -- e.g., wolves, ivory-billed woodpeckers, and grizzly bears -- have lost out.

Probably true, but this is presumably the almost-inevitable outcome when significant ecological change happens (humans clearing forests and planting crops and building towns and cities and roads and canals): species that used to be optimized for their environment are now in a different and changing environment. The ones that specialized will suffer, the generalists will be better able to adapt.

Conversely, in a stable environment, the species that develop adaptations to take advantage of the specific characteristics of that environment will thrive.

Yeah, nature has adapted to urban environments in some slightly interesting ways - but big conservation works. People who suggest otherwise should not be trusted.

Yesterday I noticed a foundation gave $9 million to spruce up a small, flood-prone portion* of one of my city's parks, that has previously been spruced up a couple times, and then allowed to deteriorate again, because we don't "do" maintenance here for some reason. $9 million could go a long way, outside the city, to do actual conservation.

*Right now it has a fairly-recent playground (the erection of which pitted children of center-city-dwelling hipsters against the cruisers who had long owned the spot - I think the children won) and a splash pad that works intermittently, when not clogged up or something; a bunch of long concrete picnic tables that date from, oh, the thirties - those things last really well! - some rockwork and landscaping, and an old "Tudor" park building that has been shuttered my thirty years here. So basically, it's already one of the pleasanter places in town. I will be glad to see the charming Tudor thing preserved - though, if history is any guide, it will remain closed anyway.

Of course, non-native plants and trees can overwhelm native forests and fuel forest fires and non-native insects can destroy native plants and trees and the animals on which they depend. As for the new "hybrids" that are flourishing, could the author be referring to an indigenous human who has "mated with like species and formed new hybrids"?

To me the last quote is analogous to "Hey, language diversity [or along any other cultural dimension] is thriving, in any country on earth never before so many different languages were spoken".

Actually language diversity has fallen as many niche languages have been lost to more dominant major languages. So an analogy might be doing a post saying something like "Yea lots of niche tribal languages are vanishing but look Star Trek invented Klingon and Tolkien made up a few languages for his Elves and Dwarfs so perhaps fictional language creation will replace language diversity!"

soon, there will be way more types of, and volume of, jelly fish in the sea. No cod, or tuna, or dolphins, but many, many, more jelly fish. So cheer up!


Rats have been doing remarkably well - and really, what are a few bird species here or there on islands anyways?

Rats are kind of the exemplar of the type of species that flourishes in an urbanized world.

When we lived in Oz there was a "green" push to exterminate ducks that were crossbreeds between native and European.

Is this basically the same story as income distributions? Distribution variance is decreasing globally but increasing at smaller spatial scales. Could these two things be tied by some pretty fundamental forces?

Obnoxious website.

"North America doesn’t have ground sloths wandering around in it today because our human ancestors killed them."

Nobody can be sure of that. There could be many other reasons for their extinction.

Literally sloths that live on the ground? I'd be proud to say that our ancestors killed off such an unfit species.

I wonder how they lasted until humans came along. You'd think they'd be fast food for other large predators. Maybe they didn't taste good?

Osteoderm armored hides plus giant claws makes for a difficult snack.

The number of species I don't know, but the number of countries, yes. Welcome to the Republic of Catalonia, and sorry for the comment almost unrelated to this post.

Chris Thomas - I believe he's been linked with that guy who's trying to turn the Nature Conservancy into "Up With People," and steering it firmly away from habitat conservation. Which speaks much louder than their professed delight in hybridization.

It is pretty plain, also: he's not a plant person. Take as but a couple examples, Chinese tallow and ligustrum - pretty sure they haven't crossed with anything, but they sure as heck have drastically reduced the diversity of, and the interest of, the native landscape in my state. Plus two, minus, oh, a thousand. And they are just obvious examples. If you like different kinds of native grasses - it's actually for once not a very good time to be alive.

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