If Australia wants to stay cool, it should stop land clearances and plant some trees

Koala bears are among the cuter victims of land clearances. Image: Getty.

Land clearance is on the rise in Australian states like Queensland and New South Wales, with land clearing laws being fiercely debated.

In Queensland in 2013–14, 278,000 hectares of native vegetation were cleared: an area 1.2 times the size of the Australian Capital Territory. A further 296,000ha were cleared in 2014–15. These are the highest rates of deforestation in the developed world.

Land clearing on this scale is bad for a whole host of reasons. But our research shows that it is also likely to make parts of Australia warmer and drier, adding to the effects of climate change.

How do trees change the climate?

Land clearing releases greenhouse gases into the atmosphere, but the effect of land clearing on climate goes well beyond carbon emissions. It causes warming locally, regionally and even globally, and it changes rainfall by altering the circulation of heat and moisture.

Trees evaporate more water than any other vegetation type – up to 10 times more than crops and pastures. This is because trees have root systems that can access moisture deep within the soil. Crops and pastures have 70 per cent of their roots in the top 30cm of the soil, while trees and other woody plants have 43 per cent of their roots in the deeper part of the soil.

The increased evaporation and rough surface of trees creates moist, turbulent layers in the lower atmosphere. This reduces temperatures and contributes to cloud formation and increased rainfall. The increased rainfall then provides more moisture to soils and vegetation.

The clearing of deep-rooted native vegetation for shallow-rooted crops and pastures diminishes this process, resulting in a warmer and drier climate.

We can see this process at work along the “bunny fence” in southwest Western Australia, where there is a moister atmosphere and more clouds over native vegetation compared with nearby farming areas during summer.

The rabbit-proof fence, which keeps pests from the rest of Australia out of the Western Australian pastoral lands. Image: Rougengineer/Wikimedia Commons.

Studies in Amazonia also indicate that, as deforestation expands, rainfall declines. A tipping point may be reached when deforestation reaches 30-50 per cent, after which rainfall is substantially reduced. Complete deforestation results in the greatest decline in rainfall.

More trees, cooler moister climate

We wanted to know how land clearing could affect Australia’s climate in the future. We did this by modelling two scenarios for different amounts of land clearing, using models developed by CSIRO.

In the first scenario, crops and pasture expand in the semi-arid regions of eastern and southwest Australia. The second scenario limits crops and pastures to highly productive lands, and partially restores less productive lands to savanna woodlands.


We found that restoring trees to parts of Australia would reduce surface temperatures by up to 1.6℃, especially in western Queensland and NSW.

We also found that more trees reduced the overall climate-induced warming from 4.1℃ to 3.2℃ between 2050 and 2100.

Replanting trees could increase summer rainfall by 10 per cent overall, and by up to 15.2 per cent in the southwest. We found soil moisture would increase by around 20 per cent in replanted regions.

Our study doesn’t mean replanting all farmed land with trees: just areas that are less productive and less cost-effective to farm intensively. In our scenario, the areas that are restored in western Queensland and NSW would need a tree density of around 40 per cent, which would allow a grassy understorey to be maintained. This would allow some production to continue such as cattle grazing at lower numbers or carbon farming.

Political and social challenges

Limiting land clearing represents a major challenge for Australia’s policymakers and farming communities. The growing pressure to clear reflects a narrow economic focus on achieving short- to medium-term returns by expanding agriculture to meet the growing global demand for food and fibre.

However, temperatures are already increasing, and rainfall is decreasing over large areas of eastern and southwest Australia. Tree clearing coupled with climate change will make growing crops and raising livestock even harder.

Balancing farming with managing climate change would give land owners on marginal land new options for income generation, while the most efficient agricultural land would remain in production. This would need a combination of regulation and long-term financial incentives.

The climate benefits of limiting land clearing must play a bigger part in land management as Australia’s climate becomes hotter and drier. Remnant vegetation needs to be conserved and extensive areas of regrowth must be allowed to regenerate.

And where regeneration is not possible, we’ll have to plant large numbers of trees.The Conversation

Clive McAlpine is a professor, Leonie Seabrook a landscape ecologist and Jozef Syktus a principal research fellow in the Global Change Institute at the The University of Queensland.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

Here are eight thoughts on TfL’s proposed cuts to London’s bus network

A number 12 bus crosses Westminster Bridge. Image: Getty.

In 2016, the urbanism blog City Observatory had a modest proposal for how American cities could sort out their transport systems: “Londonize”.

Its theory, the name of which referenced another popular urbanism blog, Copenhagenize, was that the key plank of Transport for London’s success was something that even transport nerds did not consider very sexy: its buses.

Though the Tube might get more glamorous press, London’s bus service really is impressively massive: It carries roughly 2.3bn passengers per year—much more than the Tube (1.3bn), close to the New York City subway (2.8bn), and nearly half as much as every bus service in America combined (5.1bn), while serving a population roughly 1/35 as large.

How has TfL done this? By making its bus network high frequency, reliable, relatively easy to understand and comprehensive. We rarely talk about this, because the tube map is far more fun – but the reason it’s so difficult to fall off the transport network in Greater London is because you’re never that far from a bus.

Given all that, we should probably talk about TfL’s plans to rethink – and in most cases, cut – as many as 36 different central London bus services over the next few months.

I’m not going to rehash details of the changes on which TfL is consulting from next month: there are just too many of them, and anyway it’s someone else’s scoop. The story was originally broken by Darryl Chamberlain over on 853 London; there’s also some fascinating analysis on Diamond Geezer’s blog. You should read both of those stories, though preferably not before you’ve finished reading this one.

Before offering my own analysis of the proposed changes, though, I should offer a few examples. More than a dozen routes are facing a trim: the 59 from King’s Cross back to Euston, the 113 from Oxford Circle to Marble Arch, the 171 from Holborn all the way down to Elephant & Castle and so on. A couple – the 10, the 48, the C2, and at most times the special routemaster version of the 15 – are being withdrawn altogether.

On, and one new route is planned – the 311, from Fulham Broadway to Oxford Circus. This will help plug some of the cuts to the 11, 19 and 22.

So, what does all this mean? Some thoughts:

1) This might not quite be as awful as it initially sounds

TfL says that demand for buses has fallen by around 10 per cent in London in recent years. It predicts it’ll fall further when Crossrail opens, as passengers switch to the new line, or to the tube routes relieved by the new line. So: the idea of taking some unwanted capacity out of the system is not, in itself, terrible.

Striping out unnecessary buses should also improve air quality in some of London’s worst pollution hot spots, and improve traffic flow, hopefully speeding up journeys on those buses that remain. 

A map from the presentation in which TfL explained its plans, showing the reduction in bus numbers on key arteries. Hilariously, notes Darryl Chamberlain, “It no longer produces its own maps, so has had to use one prepared by a bus enthusiast”.

The plans might even free up buses and staff to increase frequencies in outer London where demand hasn’t fallen – though these plans won’t be unveiled until next year and, for reasons I’ll come to below, I’ll believe it when we see it.

2) For many bus users, a lot of these changes will pass almost unnoticed

By my count, I use nine of the affected routes with any regularity – but only three of the changes are things that I’m likely to be at all inconvenienced by. Most of the changes either affect a part of the route I don’t take, or one where there are easy, and pain free alternatives.

This is anecdotal, obviously – perhaps I’m just lucky. But my suspicion is that a lot of these changes will go unnoticed by most passengers. It’s only the sheer number of them happening at once that makes this look like a big deal.

3) The Hopper fare makes this easier...

Once upon a time, if you had to switch buses, you had to pay a second fare. This isn’t true of journeys on the tube or railways – and since bus passengers have, on average, less money than tube passengers, it amounted to a pretty unfair tax on poorer Londoners.

But in January, in what is probably his most notable policy achievement of his two years in office so far, London’s mayor Sadiq Khan changed the rules. Now you can take as many buses as you want within an hour, for a single fare: that means you can switch buses without paying a penalty.

That will have made it easier for TfL to cut routes back: replacing a direct bus journey with one that requires a change no longer means imposing a financial penalty on passengers.


4) ...but not that easy

That’s about where the good news stops, though – because there are reasons other than cost why people prefer direct bus routes. Needing to change buses will be difficult for anyone with any form of mobility impairment, for example. Even for those of us lucky enough not to fall into that category, it’ll be annoying: it’s just easier to stay in one seat for 40 minutes than to get turfed off and have to fight for a new one halfway through.

More than that, from the passengers’ point of view, excess capacity feels quite good a lot of the time: it means your bus may well be nice and empty. Reducing the number of buses along those key corridors will also make those that remain more crowded.

5) The motive is almost certainly financial

Another of Sadiq Khan’s big policy promises was to freeze fares. He made this promise at a time when central government is massively reducing the financial support it gives TfL (the work, Chamberlain notes, of Evening Standard editor George Osborne, back when he was chancellor). And the Hopper fare, while a great idea in many ways, means a further reduction in income.

So: TfL is scrambling for cash: this is why I remain cynical about those new outer London bus routes. I would be amazed if money wasn’t a motivation here, not least because...

6) TfL thinks no one will notice

Any attempt to reduce tube frequencies, let alone close a station, would result in uproar. Hashtag campaigners! Angry people pointing at things in local newspapers! Damning reports on the front of the Evening Standard from the bloke who made it happen!

Buses, though? Their routes change, slightly, all the time. And do you really notice whether your local route comes every 10 minutes or every 12? That’s not to mention the fact that bus passengers, as previously noted, tend to be poorer – and so, less vocal – than tube passengers.

So cuts, and the savings they bring, are much easier to sneak through. TfL probably would have gotten away with it, too, if it hadn’t been for those meddling bloggers.

Although...

7) Scrapping the C2 might be a mistake

The C2 runs from Parliament Hill, through Kentish Town and Camden to Oxford Circus. In other words, it links north London, where a lot of journalists live, to the offices of the BBC and Buzzfeed.

As occasional New Statesman writer James Ball notes, this is probably not the easiest route to quietly shelve.

8) None of this is set in stone

The consultation doesn’t even begin until next month and then will run for six weeks – so all these plans may yet be forgotten. We shall see.

Anyway – here’s Darryl Chamberlain’s original scoop, and here’s some detailed analysis on Diamond Geezer. Please support your local bloggers by reading them.

Jonn Elledge is the editor of CityMetric. He is on Twitter as @jonnelledge and on Facebook as JonnElledgeWrites.

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