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.

 
 
 
 

“Residents were woken by the sound of bulldozers”: in Lagos, gentrification can mean midnight demolition

A displaced family sits on make-shift structures after their home in the waterfronts was demolished last November. Image: Getty.

The ambitious plans produced by the Lagos state government to redevelop the most populous city in Africa are often lauded in Nigeria. Moving around in this buzzing yet often dysfunctional commercial capital is often tortuous, with thick traffic and poor connectivity problems across the city.

The current state governor, Akinwunmi Ambode, wants to remake the city’s image, turning it from a sprawling bottleneck of a city to a better structured and more functional one. But his plans to improve infrastructure and redevelop large parts of the city have had sinister consequences for swathes of the city’s population: the urban poor, who seem to have no place in Ambode’s vision.

The last few years have seen an alarming trend of state-backed destruction of small businesses, markets and especially informal housing settlements, “regenerating” areas with new expensive housing and development. Last year a large fishing community in Lagos informally called the ‘waterfronts’, housed over 300,000 people. But in the last five months, three rounds of demolitions have ruthlessly left more than 35,000 people homeless.

In November, the homes of over 30,000 people were destroyed by bulldozers. Last week a further 4,700 people were the victims of sudden midnight demolitions. According to residents, the destruction was supervised by state officials and police. A High Court ruling the previous January had said that previous demolitions by the state were “inhumane” and against the residents’ human rights, mandating all parties to enter mediation. All the same, residents were woken up by the sound of bulldozers which destroyed their homes, with no notice to collect their belongings.

Demolitions like this have become increasingly commonplace in Lagos, where land is scarce and valuable. By some estimates, over two thirds of people in Lagos live in informal housing settlements. And not only is there a premium on expensive housing projects; many of the state’s big infrastructure plans, like the desperately needed bridge connecting the Island to the mainland, cut through areas filled with such settlements.

After demolitions, many residents simply move to the outskirts of their destroyed communities or to other informal settlements. The cost of setting up shelters to live in is far more is feasible than formal housing costs.

Too often the government prefers to evict and demolish rather than mediate. It rarely provides assistance for tenants to move, or regulates and redevlops those areas with them in mind.  After a kidnapping near the waterfronts, the governor of Lagos, Akinwunmi Ambode, described the communities as “the abode of miscreants/street-urchins, kidnappers, touts, street traders and hawkers”. In his vision of a modern Lagos, slums and street sellers have little place.


A closing market

Government policies have also made it increasingly hard for the urban poor to work. In many settlement areas, small markets spring up to cater to the communities that live there. Small businesses also set up in other areas that aren’t approved, or in complexes rented from landlords who aren’t transparent with tenants about ownership disputes.

On side streets, women sell items laid on fabric or stools. And on the streets of Lagos, young men and women, and sometimes children, weave dangerously between impatient motorists: the gridlocks that hurt the city present a ready market for those selling anything from drinks and snacks, to underwear or household furniture.

Officially a ban on street trading has been in place in Lagos since 2003, but in the last year, in certain key areas, it has been more keenly enforced. Millions of families rely on street trading for income, yet its dangers and problems are clear. Here too, instead of reforming a system that millions of people rely on, the government wants to end it entirely. State officials have in the last year targeted key areas, arresting street sellers and confiscating their goods.

The government claimed that, after the ban, street traders would be able to access loans to start more formal businesses. But poor capacity, access and loan requirements have made it a out-of-reach for many traders.

Gentrification is a hallmark of major cities all over the world. But in Lagos, to many of the city’s poor, it’s manner is particularly violent and cruel.

The governor is keen to be the face of a new Lagos, attracting and administering new redevelopment projects. But he is not prepared to work out how to rehouse or compensate the people whose lives are being torn apart by such plans. He wants Lagos to be more ordered, for selling on the street to move into more regulated areas. But as the space for those areas diminishes to make way for shopping malls, and the costs outstrip people’s resources, there are many reasons why people aren’t selling there in the first place.

Regenerating and reforming Lagos is not a problem in itself. But the disregard for many of the people who live there is fuelling needless suffering.

Want more of this stuff? Follow CityMetric on Twitter or Facebook.