ABOUT THIS EPISODE

Evolution in cities is happening faster than Darwin could have imagined
English
Canada

TRANSCRIPT

00:00:02this is a CBC podcast and that in audio form kind of summarizes recent history on earth nature giving way to the concrete jungle plants and animals being pushed aside and replaced by the noisy products of industry but you just can't stop evolution for three billion plus years life
00:00:44on our planet has been adapting to new conditions in changing environments it's adopted to mass of climate change to planet killing asteroid impacts to tectonic shifts where the very ground has changed as continents are remade well now life is adapting to what might be the trickiest set of
00:01:02new conditions of all we build giant sprawling cities of brick glass and concrete canyons made of great buildings and immense desert of asphalt but evolution is not to be denied as we've made this new urban landscape natural life has found a way to colonize and adapt to it
00:01:21a few examples urban song birds have changed their color their sound even their mating habits in order to survive foxes have adapted to living in the busiest cities in the world plants have developed new types of seeds that allow for growth in cracks in city sidewalks those are
00:01:41just some of the examples doctor mental skills Hausen illustrates in his new book Darwin comes to town how the urban jungle drives evolution doctor skilled Hausen is an evolutionary biologist ecologist and professor of bio diversity at Leyden university in the Netherlands hello welcome the Cork uncorks hello Bob
00:02:00thank you very much for having me %HESITATION first what what fascinates you about this question of life adapting to our urban environments well a couple of things to begin with it's very rapid evolution we've we're we're really observing species adapting almost as we speak much faster than them
00:02:18we tend to think evolution takes place %HESITATION and that's because cities are so different from natural environment that it creates a situation that requires very drastic adaptation that usually means very fast it up Tatian but also because cities are really expanding rapidly on the earth and it's really
00:02:38becoming a habit that in its own right three becoming part of the earth's surface that is therefore species to colonize it can all be ignored anymore so I think in the in the near future we're going to see a lot of wildlife being forced to adapt or go
00:02:55extinct and of course both things happen but in in my book I I focus on the adaptation on the species that managed to survive in cities thanks to Darwinian adaptation well it is remarkable in your book how many species have adopted because we tend to think of cities
00:03:10as kind of a sterile environments where we clean away anything that's living in there's something growing we cut it off or clean it how have cities become so rich in biodiversity well it's a number of things first of all not all species can live in cities there are
00:03:26lots of species that really need pristine natural habitats and they cannot survive in cities so little species do disappear when the city arises in a place but also a lot of species managed to survive and there's several reasons how they could do that for some are simply we
00:03:43collect pre adapted they find something in the city that resembled their natural habitats think of rock pigeons for example that the city pigeons are originally rock pigeons they they live in very very rocky cliff the environments and to them our city with with its buildings is not that
00:04:00different from the natural %HESITATION rocky environment but also cities are actually quite diverse if you compare them to the rural countryside nowadays especially in North America and Europe where almost every maximum productivity squeezed out of every inch of lands there's not much natural habitat left in the countryside
00:04:19for species to survive where where its cities are full of interesting links little pockets of vegetation gardens I mean the the cities are consist of thousands and thousands of backyard which are all different and especially for plants and insects that creates a lot of diversity of habitats that
00:04:35they can live in and then of course you have the real evolution of species that are invading cities and adapt as they invade and evolve a new niche well you say in your book that cities are like mad scientist creating their own ecological concoctions what you mean by
00:04:52that yeah that's another thing that of course we we humans bring in a lot of species I mean some species come into the city under their own steam but but some are brought in by us %HESITATION of course our gardens are planted full of species that come from
00:05:07all corners of the globe bets and %HESITATION and pests are introduced accidentally or intentionally by people ends cities are really a melting pot of species from all over the world which are forced to find a way to live together and and so %HESITATION %HESITATION blonde from South America
00:05:25can suddenly meets an insect from from Europe in in a in a city in China and find out that that the insect can eat the blonde if it adapts to this blog and that's really where this adaptation this is happening that these species are meeting other species that
00:05:42they've never met before and that haven't evolved to deal with these PC set to but to to use those opportunities they must adapt and they do adapt well you mentioned how cities create their own sort of micro Kassem's little ecosystems of the wrong such as %HESITATION the parks
00:05:58in New York City were mice isn't doing quite well and and the parts are all different tell me about that yeah %HESITATION one of the things about cities is that there's a lot of fragmentation going on so in the in natural environments of course you can find vast
00:06:11forests that are sort of uninterrupted over a large area in cities of these bits of vegetation very much fragmented so New York City is a good example where of course four hundred years ago there was a continuous forest covering Manhattan and the the the five boroughs and all
00:06:27of that forests all that is left now are are city parks likes like Central Park and Prospect Park does our bits of origin of education in the still bits of orginal fauna that survive isolated from each other in these are marooned in these pockets of all forest in
00:06:43the city and the white footed mouse is one of the native rodents that live in in the east coast US that are surviving have have been surviving in these isolated bits of forest and in contrast to wild my living in the countryside these mice in New York City
00:07:00are that putting to their individual parks that they live in so that their genes are actually changing to suit the conditions in those specific parks for example in Central Park the mice have evolved genes that help them deal with a very fatty diets which of course has to
00:07:15do with all the junk food that people leave behind in the parking that these mice eat in another park there's a gene that has changed their immune system probably because there was some some epidemic possibly brought in by by humans or other animals that has spread in that
00:07:29park and has has made this population of mice resistant to that particular disease so every pockets off habitat in the city has its own signature it has its own little little %HESITATION Darwinian landscape that species adapt to well you have so many examples of plants and animals making
00:07:47genetic adaptations for urban life in your book it's %HESITATION we can't go through the mall do you have any favorites what I really like is an example from Europe that's the the European blackbirds it was one of the first birds to invade cities already in the early nineteenth
00:08:01century in Germany and in Rome and from then on that has become more and more urban even though the forest blackbird still still survive they still exist and it turns out that those urban black birds in the forest black birds over this two hundred years have become more
00:08:16and more different and it's not just a single thing in which they're different is really a whole portfolio off of differences in the way they look for example they have shorter beaks in the city and the shorter intestines also the way they sing they sing at a higher
00:08:31pitch which probably has to do with the urban noise from traffic he also sings during the night which the force blackbird doesn't do in the urban situation they don't migrate anymore they stay in the city the whole year round because there's always food available where state forest like
00:08:45bridge they migrate away during the winter to the south to the extent that these urban and forest black birds are not really into reading anymore not mixing with each other which for example has to do with the fact that my great and is different as I mentioned said
00:08:59by the time the fourth leg was come back from their winter quarters to urban black birds have already started breeding because they are yeah that it's warmer in the city because of the circle urban heat island and there's food two year round so they can start breeding in
00:09:11March already where is the forest like birds only started mace additional genes being exchanged anymore because between the forest and the urban black bird so this is really a bird that's on the way of becoming a separate species so you're saying the same thing in these black birds
00:09:27with their different beaks and all that between the urban and the rural that Darwin saw with finches in the Galapagos islands exactly now there was another bird that %HESITATION has adapted to city life by using cars to crack not healthy felt that yep that's right those are a
00:09:45carrion crows in Japan that they have for a long time have been using the Japanese Walmart's as food and they've been dropping those from from a great height they pick them up from the tree and then they fly to ten meters high and the drop them on the
00:09:59rock and then they've lost cracks and they can eat the inside than cities became available in this continue doing that but then dropping the the double knots on too tarmac and onto the streets to correct them and one points in in the nineteen seventies it was discovered that
00:10:15in the city of Sendai in northern Japan I was in a population of carrion crow said wins one step further and they started dropping these notes in front of the wheels of passing cars which was much easier to crack them of course they didn't need to fly high
00:10:30up and dropped enough to repeatedly to until it broke it is just place it in front of the wheels of a passing car and even stationed themselves at the pedestrian crossing so when the car stopped that would help into the streets drop a few of those notes in
00:10:43front of the cars and when the lights turned on the car started moving they would come back and pick up the flesh and this this is of course is not yvolution in the sense that there is a gene for this behavior and this behavior spreads in that city
00:10:57and outside the city probably because birds were imitating each other but there are genes for personality traits in birch which makes them more curious more inventive more better at problem solving and we do see that birds and mammals in general in in cities are evolving in those personality
00:11:15traits to become more curious %HESITATION less fearful of humans better at solving unfamiliar problems and probably this is a situation where we see that happening in these crows right now there is one other example that %HESITATION you show in your book about %HESITATION adaptation to urban life that
00:11:34I found really fascinating it wasn't burrs was Miskito who's living underground in London tell me about that yeah the London Underground mosquitoes actually one of the one of the most famous examples it's also a situation that looks like the evolution of an entirely new species similar to the
00:11:50%HESITATION European black bird %HESITATION and they do things which they do very differently from their closest relative which is an above ground mosquito for example the above ground Miskito mostly feeds on bird blood where's the underground mosquito feeds on human blood above ground they make these big swarms
00:12:07two mates on the ground is just one on one meeting %HESITATION and there are a number of other differences and it seems that all those differences have evil they're really since people started building underground structures and living or at least commuting underground in subways but also living and
00:12:25congregating in cellars and basements %HESITATION and this has happened all over the world so these these above ground mosquitoes in probably in the past few hundred years have spawned a new species of mosquito that is adapted to living underground and feeding on on human blood and in London
00:12:41they've even study the genes of those mosquitoes and figured out that the populations of mosquitoes in different subway lines are also different just like those those mice in the New York parks that are adapting to the individual parts there's mosquitoes indifference metro lines that are adapting to different
00:12:57metro lines in there that don't mix anymore because those lines are separate and they would all need to change at Oxford Street station to make genetically which they don't so yeah it's also very nice example of of urban evolution in the in a very any insect that very
00:13:12few people pay any notice well there are so many adaptations in so many species but there are also some things that some animals just can't seem to adapt to searches birds running into windows why is that yeah %HESITATION this the large death rates shoot result in the evolution
00:13:32of course evolution works by natural selection which means that some animals survive other animals don't and the ones that don't survive %HESITATION in this case are the ones that hits these building so you would expect that birds that are able to see glass better or not being confused
00:13:47by light at night are the ones that have an evolutionary advantage and should be passing on their genes to make birds less and less prone to being killed by these glass windows but that doesn't seem to be happening this seems to be some at least as far as
00:14:01we can tell that doesn't seem to be a decline in bird deaths because the birds are evolving to stay away from plastic keep dying by by numbers and it could be that see yeah these things are so hard wired in their in their brains and in their behavior
00:14:16deaths %HESITATION yvolution cannot change this of course form for almost the entire history of of life on earth the only lights at nights has been the stars and the moon and only very recently people have started you know lighting up the night sky with artificial lights and a
00:14:34lot of insects and birds that my grades at nights get confused by these lights the the %HESITATION used to use the moon to fly in a straight line and now suddenly have moons everywhere artificial moons that they get confused by and the the tribute in light memorial off
00:14:50the nine eleven attacks was or is every year two beams of light very powerful scene on lights that are beaming up into the sky and recreating the two towers in this sort of a ghostly ephemeral specter but this is of course nine eleven so it's it's the middle
00:15:08of September it's the pinnacle of the altar migration of warblers along the east coast of the U. S. and these warblers my great at nights probably because that's the time when they're least likely to be called by sparrowhawks for example which witch hunt by day time ends they
00:15:26tend to focus in the geographical funnel said a tip of Manhattan is where they old old US flight pots congregates and the result is that every every year when they light up this memorial there are hundreds literally thousands of birds that are get called in these keys cages
00:15:44of lights and come fluttering down and and probably dying %HESITATION in large numbers so it's it's a very poignant way of of showing how everything we do as humans a fax %HESITATION the wildlife that's why I think you can never use this process of adaptation as an excuse
00:16:05to remove natural habitats I think we're still going to need does natural habitat for the survival of a large chunk of by diversity but there is a smaller jungle by diversity that will be able to live with us in cities and create an entirely new urban human adapted
00:16:19ecosystem doctor skilled house in thank you for the book and thank you for your time thank you very much for having me doctor mental skilled Hausen is an evolutionary biologist ecologist and professor of bio diversity at Leyden university in the Netherlands his new book is Darwin comes to
00:16:37town how the urban jungle drives evolution for more CBC podcasts go to CBC dot CA slash podcasts

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