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.

 
 
 
 

The tube that’s not a tube: What exactly is the Northern City line?

State of the art: a train on the Northern City Line platforms at Moorgate. Image: Haydon Etherington

You may never have used it. You may not even know that it’s there. But in zones one and two of the London Underground network, you’ll find an oft-forgotten piece of London’s transport history.

The Northern City line is a six-stop underground route from Moorgate to Finsbury Park. (It’s officially, if confusingly, known as the Moorgate line.) But, unlike other underground lines, it not part of Transport for London’s empire, and is not displayed on a normal tube map. Two of the stations, Essex Road and Drayton Park, aren’t even on the underground network at all.

The line has changed hands countless times since its creation a century ago. It now finds itself hiding in plain sight – an underground line, not part of the Underground. So why exactly is the Northern City line not part of the tube?

The Northern City line, pictured in dotted beige. Source: TfL.

As with many so many such idiosyncrasies, the explanation lies in over a century’s worth of cancellations and schemes gone awry. The story starts in 1904, when the private Great Northern Railways, which built much of what is now the East Coast Main Line, built the line to provide trains coming from the north of London with a terminus in the City. This is why the Northern City line, unlike a normal tube line, has tunnels wide enough to be used by allow mainline trains.

Eventually, though, Great Northern decided that this wasn’t such a bright idea after all. It mothballed plans to connect the Northern City up to the mainline, leaving it to terminate below Finsbury Park, scrapped electrification and sold the line off to Metropolitan Railways – owners of, you guessed it, the Metropolitan line.

Metropolitan Railways had big plans for the Northern City line too: the company wanted to connect it to both Waterloo & City and Circle lines. None of the variants on this plan ever happened. See a theme?

The next proposed extensions, planned in the 1930s once London Underground had become part of the domain of the (public sector) London Passenger Transport Board, was the Northern Heights programme. This would have seen the line would connected up with branch lines across north London, with service extended to High Barnet, Edgware and Alexandra Palace: essentially, as part of the Northern line. The plans, for the main part, were cancelled in the advent of the Second World War.

The Northern Heights plan. The solid green lines happened, the dotted ones did not. Image: Rob Brewer/Wikimedia Commons.

What the war started, the Victoria line soon finished. The London Plan Working Party Report of 1949 proposed a number of new lines and extensions: these included extension of the Northern City Line to Woolwich (Route J) and Crystal Palace (Route K). The only one of the various schemes to happen was Route C, better known today as the Victoria line, agreed in the 1950s and opening in the 1960s. The new construction project cannibalised the Northern City Line’s platforms at Finsbury Park, and from 1964 services from Moorgate terminated one stop south at Drayton Park.

In 1970, the line was briefly renamed the Northern Line (Highbury Branch), but barely a year later plans were made to transfer it to British Rail, allowing it to finally fulfil its original purpose.


Before that could happen, though, the line became the site of a rather more harrowing event. In 1975, the deadliest accident in London Underground history took place at Moorgate: a southbound train failed to stop, instead ploughing into the end of the tunnel. The crash killed 43 people. The authorities responded with a major rehaul of safety procedure; Moorgate station itself now has unique timed stopping mechanisms.

The last tube services served the Northern City Line in October 1975. The following year, it reopened as part of British Rail, receiving trains from a variety of points north of London. Following privatisation, it’s today run by Govia Thameslink as the Great Northern route, served mainly by suburban trains from Hertford and Welwyn Garden City.

Nowadays, despite a central location and a tube-like stopping pattern, the line is only really used for longer-scale commutes: very few people use it like a tube.

Only 811,000 and 792,000 people each year enter and exit Essex Road and Drayton Park stations respectively. These stations would be considered the fifth and sixth least used in the tube network – only just beating Chorleywood in Hertfordshire. In other words, these usage stats look like those for a station in zone seven, not one in Islington.

One reason for this might be a lack of awareness that the line exists at all. The absence from the tube map means very few people in London will have heard of it, let alone ever used it.

Another explanation is rather simple: the quality of service. Despite being part and parcel of the Oyster system, it couldn’t be more different from a regular tube. The last (and only) time I used the line, it ran incredibly slowly, whilst the interior looked much more like a far-flung cross-country train than it does a modern underground carriage.

Waiting for Govia. Image: Haydon Etherington.

But by far the biggest difference from TfL is frequency. The operators agreed that trains would run between four and six times an hour, which in itself is fine. However, this is Govia Thameslink, and in my experience, the line was plagued by cancellations and delays, running only once in the hour I was there.

To resolve this, TfL has mooted taking the line over itself. In 2016, draft proposals were put forward by Patrick McLoughlin, then the transport secretary, and then mayor Boris Johnson, to bring "northern services... currently operating as part of the Thameslink, Southern and Great Northern franchise" into TfL's control by 2021.

But, in a story that should by now be familiar, Chris Grayling scrapped them. At least it’s in keeping with history.