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.

 
 
 
 

A warped mirror: on gentrification and deprivation on London’s Caledonian Road

The London Overground crosses Caledonian Road. Image: Claude Lynch.

Capital cities are, more often than not, a focal point for the stark divide between rich and poor – places where the most economically deprived meet the most economically empowered. In London, these divides can be more than stark: they can be close, even intimate, and there are districts where crossing the street can be like entering a different world. One such street is the Caledonian Road.

Known local as “the Cally”, Caledonian Road runs for about a mile and a half, from Kings Cross to the Nags Head junction in Holloway, and was built in 1826 to provide a new arterial route to the north from the West End. At first, developments on the road were sparse; among the first notable buildings were the Royal Caledonian Asylum, which gave the road its name, and H.M. Prison Pentonville.

For some time, the northern half of the road was seen as far removed from central London, which stymied development. It wasn’t until the latter half of the 19th century residential development really got going. By the time Caledonian Road station opened on the Piccadilly line in 1906, the area was flush with Victorian terraces.

These, though, mainly lay on the eastern side. To the west, the proximity of King’s Cross prompted the development of heavy industry, particularly the clay kilns that were helping to build Victorian London proper. The divide had begun:  the east side of the street, the area known as Barnsbury, was notably quieter and calmer than the west side. Ever since the 19th century, the ‘V’ formed by Caledonian Road and York Way has been known for a high incidence of gang violence and social problems.

As in many parts of London, the end of the Second World War brought a chance to start from scratch. Many of the slums to the west of the Cally had been bombed to smithereens, and those that remained still lacked gas and hot water.

But this was the era of municipal dreams: Islington council cleared the slums and constructed the Bemerton Estate. Instead of reflecting the industrial history of the area, the estate reflected Barnsbury back at itself, treating Caledonian Road as some sort of warped modernist mirror. The square gardens of Barnsbury were reimagined as the spaces between the highrises of Bemerton, and this time, they were actually square.

The estate was immediately popular, its open design prompting a renewed sense of community in the west. But it didn’t last.

Square gardens on one side, not-so-square on the other. Image: Google Maps/CityMetric

As far back as the 1950s, Islington had already become synonymous with gentrification. Forty years later, before moving to Downing Street, Tony Blair’s London residence was Barnsbury’s leafy Richmond Crescent. House prices in the area have gone through the roof and now Barnsbury is mainly home to a the professional elite.


At the same time, though, Caledonian Road’s warped mirror has given Bemerton the exact opposite: in spite of attempts to rejuvenate it, downward spiral of deprivation and antisocial behaviour have blighted the estate for some time The promise of inviting square gardens and communal living has been inhibited by crime and poverty; the gardens lie empty, while those in Barnsbury thrive.

The disparity of wealth across Caledonian Road is regrettable. That’s not just because it speaks to a wider segregation of London’s rich and poor – a phenomenon exemplified last year by the Grenfell Tower fire in Kensington & Chelsea, the richest borough in Britain. It’s also because, in the Bemerton Estate, planners had thought they saw an opportunity to offer more Londoners the idyll of square gardens and leafy streets, often reserved for the richest.

It might be too much to claim the estate as a failure; events such as the Cally Festival aim to bring together both sides of the road, while other council programmes such as Islington Reads help to foster a greater sense of neighbourhood.

Road should never divide us; rather, they should unite those who live on either side. The spirit of Caledonian Road should cross the gap – just like the railway bridge that bears its name.