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How the warming world could turn many plants and animals into climate refugees
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Finding the optimum environment and avoiding uninhabitable conditions has been a challenge faced by species throughout the history of life on Earth. But as the climate changes, many plants and animals are likely to find their favoured home much less hospitable.
In the short term, animals can react by seeking shelter, whereas plants can avoid drying out by closing the small pores on their leaves. Over longer periods, however, these behavioural responses are often not enough. Species may need to migrate to more suitable habitats to escape harsh environments.
During glacial times, for instance, large swathes of Earth’s surface became inhospitable to many plants and animals as ice sheets expanded. This resulted in populations migrating away from or dying off in parts of their ranges. To persist through these times of harsh climatic conditions and avoid extinction, many populations would migrate to areas where the local conditions remained more accommodating.
These areas have been termed “refugia” and their presence has been essential to the persistence of many species, and could be again. But the rapid rate of global temperature increases, combined with recent human activity, may make this much harder.
Finding the refugiaEvidence for the presence of historic climate refugia can often be found within a species’ genome. The size of populations expanding from a refugium will generally be smaller than the parent population within them. Thus, the expanding populations will generally lose genetic diversity, through processes such as genetic drift and inbreeding. By sequencing the genomes of multiple individuals within different populations of a species, we can identify where the hotbeds of genetic diversity lie, thus pinpointing potential past refugia.
My colleagues and I recently investigated population genetic diversity in the narrow-leaf hopbush, a native Australian plant that got its common name from its use in beer-making by early European Australians. The hopbush has a range of habitats, from woodlands to rocky outcrops on mountain ranges, and has a wide distribution across southern and central Australia. It is a very hardy species with a strong tolerance for drought.
We found that populations in the Flinders Ranges have more genetic diversity than those to the east of the ranges, suggesting that these populations are the remnants of an historic refugium. Mountain ranges can provide ideal refuge, with species only needing to migrate short distances up or down the slope to remain within their optimal climatic conditions.
In Australia, the peak of the last ice age led to dryer conditions, particularly in the centre. As a result, many plant and animal species gradually migrated across the landscape to southern refugial regions that remained more moist. Within the south-central region, an area known as the Adelaide Geosyncline has been recognised as an important historic refugium for several animal and plant species. This area encompasses two significant mountain ranges: the Mount Lofty and Flinders ranges.
Refugia of the futureIn times of increased temperatures (in contrast to the lower temperatures experienced during the ice age) retreats to refugia at higher elevations or towards the poles can provide respite from unfavourably hot and dry conditions. We are already seeing these shifts in species distributions.
But migrating up a mountain can lead to a literal dead end, as species ultimately reach the top and have nowhere else to go. This is the case for the American Pika, a cold-adapted relative of rabbits that lives in mountainous regions in North America. It has disappeared from more than one-third of its previously known range as conditions have become too warm in many of the alpine regions it once inhabited.
Further, the almost unprecedented rate of global temperature increase means that species need to migrate at rapid rates. Couple this with the destructive effects of agriculture and urbanisation, leading to the fragmentation and disconnection of natural habitats, and migration to suitable refugia may no longer be possible for many species.
While evidence for the combined effects of habitat fragmentation and climate change is currently scarce, and the full effects are yet to be realised, the predictions are dire. For example, modelling the twin impact of climate change and habitat fragmentation on drought sensitive butterflies in Britain led to predictions of widespread population extinctions by 2050.
Within the Adelaide Geosyncline, the focal area of our study, the landscape has been left massively fragmented since European settlement, with estimates of only 10% of native woodlands remaining in some areas. The small pockets of remaining native vegetation are therefore left quite disconnected. Migration and gene flow between these pockets will be limited, reducing the survival chances of species like the hopbush.
So while refugia have saved species in the past, and poleward and up-slope shifts may provide temporary refuge for some, if global temperatures continue to rise, more and more species will be pushed beyond their limits.
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Matt Christmas does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.
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End of the road? Why it might be time to ditch your car
The average car is stationary 96% of the time. That’s a fairly consistent finding around the world, including in Australia. A car is typically parked at home 80% of the time, parked elsewhere 16% of the time, and on the move just 4% of the time. And that doesn’t include the increasing time we spend at a standstill in traffic.
Bill Ford, executive chair of the Ford Motor Company, says we’re heading for “global gridlock”. And he’s not alone in saying we cannot simply keep adding more cars to our roads.
The funny thing is that while we own more cars than ever, we’re actually using them less. You might think that’s a good thing; that we’re responding to worsening congestion and health, debt and environmental damage by opting to drive fewer kilometres.
But the problem is, we’re still choking our cities and harming our health, finances and environment by continuing to waste our resources on these increasingly dormant vehicles.
It’s not just the car itself that’s wasted. Consider the resources and infrastructure – both private and public – needed to design, mine, manufacture, ship, sell, fuel, move, store, secure, insure, regulate, police, maintain, clean, repair and dispose of all these cars.
David Owen, a staff writer with The New Yorker, has called cars “consumption amplifiers”. They are emblematic of a hyper-consumerist lifestyle that doesn’t really make us any happier.
Our declining car use gives us an opportunity. If we can adjust our car ownership patterns to match our actual needs, we can plan our lives and cities in ways that don’t revolve around a mode of transport that no longer serves us like it used to.
Fast cars?By default, we still think of cars as fast and convenient. It might appear that way on the street, but the overall reality is quite different.
For a start, cars are a woefully inefficient way to transport a person from A to B. Typically, only around 20% of the energy from fuel combustion is converted into motion.
If we assume that the average car weighs roughly 20 times more than its driver, we can estimate that for a single-occupant car journey, with no significant other cargo, the effective fuel efficiency drops to just 1% (adding a passenger only raises this to 2%). And that’s before we take into account the broader resource and infrastructure requirements, as mentioned above, for that journey to take place.
The urban car isn’t terribly fast either. Research shows that when we take into account not only the time in transit but also the time spent working to pay for the car and its operation, the car’s average “effective speed” in cities is generally well under 13km per hour. This has been called the “urban speed paradox”. As cyclist and author Greg Foyster has pointed out, “your typical commuting cyclist can beat that without breaking a sweat”.
These and other factors have resulted in what’s called “peak car”. The average distance travelled per person by car has been declining for more than a decade. Commuting distances and average urban driving speeds have also peaked and the rate of new licences is plummeting.
Ford Motor Company’s future trends manager, Sheryl Connelly, has suggested that cars no longer symbolise freedom to this generation in the way they did to baby boomers. The rise of car-sharing schemes has also caused renting to lose its stigma. Young people now prize access over ownership.
Yet, for too many of us, a privately owned car remains the default for almost every transport task. There are times when cars are useful, but for general urban commuting, based on what we’ve seen above, it is like using a chainsaw to carve butter.
Expanding the transport toolkitMany urban areas around the world are seeing a rapid shift away from private cars as the dominant form of transport. Areas of some cities are even going car-free while reallocating old road space to public or active transport, or back to nature.
In Australia, the City of Port Phillip has devised a plan to halt the growth in car ownership, even as the city’s population doubles, by converting hundreds of parking spots into car-share bays. Each share-car is reported to take up to 14 cars off the road, while cutting the costs of personal mobility by up to 60%.
One local resident was reported as saying the recent addition of a car-share spot at the end of his family’s street had prompted them to sell their rarely used car. “Now that there is a really good number of cars close by, we can make that move to going completely car-free.”
Then there’s the rapid development of other shared transport such as bike-share programs. By 2014, the number of cities with bike-share programs had increased to 850, up from only 68 in 2007.
Alongside all this are new planning models for activity centres, integrated transport networks, and carless or near-carless residential developments.
All the while, speed limits are decreasing, free public transport (at point of access) is increasing, and automobile and business associations are advocating for heavy investment in active and public transport.
Transport in 2017 and beyondNone of this is meant to demonise cars or their drivers, or to suggest that no one should own a car. What I am saying is that the model of everyone owning their own car is best relegated to the 20th century. This leads to the question of what the optimal level of car ownership might be, where we achieve the transport benefits without the waste, damage and expense.
What if in 2017 we focused on developing our personal and collective toolkits beyond the chainsaw, to do a better job of moving ourselves around?
You might get to know your local matrix of transport options better, from walking, cycling and skating routes to public transport, shared transport (car-share, ride-share, bike-share, taxis) and rented transport (cars, trucks, motorbikes, bicycles). Over time, you could then home in on how they work best together.
More of us could consider placing our cars in peer-based car-share or ride-share programs (informal or formal). Or we could even choose to sell our cars, and opt into one of the above schemes as a user rather than provider.
Peak car is upon us, and with it comes the opportunity to choose new models of urban transport that better match our current needs for quality, sustainable living. It is vital work. And like any good tradie, we need to make sure we have the right tools for the job.
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Anthony James does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.
Caroline Lucas’s error in voting to hold the EU referendum | Letters
Caroline Lucas MP rightly points to “a cocktail of threats” to the environment from leaving the EU (A ‘green guarantee’ could stop Brexit ruining our environment, theguardian.com, 13 February). She neglects to mention her own role in bringing on these threats: the vote she cast to hold the EU referendum in the first place. In her statement to the Commons on 9 June 2015, when the EU referendum bill was under review, she pointed to the EU’s many environmental protections; called nonetheless for its “radical reform”; noted that achieving this “by walking away from the EU makes no sense at all”; and then, along with hundreds of other pro-remain MPs, invited the voters to walk away. It was a classic muddle of cross-purposes all too familiar from the left on Europe.
At the time, Lucas could have demanded, or at least suggested, that the likely environmental and other costs be specified and advertised to the public ahead of any Brexit vote. Instead she agreed to a simple in/out vote with no further conditions. So perhaps she means to say that the “real fight starts now”?
Jeff Smith
Brno, Czech Republic
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A group of scimitar-horned oryx, an antelope declared extinct in the wild, have been reintroduced to their original home on the edge of the Sahara desert.
Fourteen captive-bred animals were released in a remote area of Chad and joined a first group reintroduced in August 2016, conservationists from the Zoological Society of London (ZSL) said.
Continue reading...Underwater photographer of the year 2017 winners – in pictures
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