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.

 
 
 
 

Pembrokeshire's innovative new eco-hamlet is great. But it should be the size of a city

The eco hamlet. Image: Western Solar.

The opening in January 2017 of an “eco-hamlet” for council house tenants in West Wales is great news. I have nothing but praise for a development which builds houses with a low carbon footprint, using locally grown wood, to make homes which are well insulated and powered by solar energy. It was also quick to build, with large sections being made in a factory and then assembled on site. And it was relatively cheap – at around £70,000 to £100,000 per building, it is certainly comparable to the costs of more conventional builds.

These houses are an inspiration to the construction industry and an aspiration for the home owner. After all, who wouldn’t like to live in a house that had yearly utility bills of £200, rather than the national average of £1,500?

So the problem is not the six wonderful solar houses at Glanrhyd, Pembrokeshire, or the lucky people who will get to live in them (and enjoy shared use of an electric car). The problem is that we’ve seen all of this before – but nothing changes. What we really need is far, far more of them.

Pentre Solar in Pembrokeshire. Image: Western Solar.

I’ve been involved in sustainable construction for nearly 25 years and seen many inspirational developments like Glanrhyd. There’s Julian Marsh’s home in Nottingham, Susan Roaf’s Oxford Ecohouse and the Hockerton Housing Project, to name but a few. The list is long.


Yet while many individuals continue to build these innovative and inspirational structures, we have a construction industry which still responds to these buildings with disdain. One executive from a large well-known house building company told me recently: “This is a new, expensive and untested technology. We just can’t risk building something so new with all the risks to the consumer and at a higher cost.”

But the situation is even worse than the disdain from the mainstream construction industry. Rather than being welcomed, the latest versions of these sustainable buildings are challenged at every turn. The initial response to the Welsh eco-hamlet plans were concerns about the materials, the technology and the design. The houses at Glanrhyd then had more than 20 planning conditions placed upon them. The CEO of Western Solar, the company behing the hamlet, freely admits that nearly half of their research budget went on solving problems they encountered along the way.

Thinking and building big

So it seems this kind of development just isn’t celebrated enough. There is a general atmosphere of mistrust from construction professionals. It is seen as too complex, too expensive, too risky. Yet there are positive reactions, too. Welsh politician Lesley Griffiths had this to say about the new houses in Glanrhyd:

This scheme ticks so many boxes. We need more houses, we need more energy efficiency, we want to help people with fuel poverty. It’s been really good to hear how they have sourced local products. It’s great they’re using local people to build the houses.

Surely we need to take the eco-technology we have and start rolling it out on a much larger scale. To do so would be a massive step in meeting the significant housing shortage (an estimated 125,000 extra new houses are needed every year). It would also address the disrepair of our current housing stock, and help refit the millions of houses in good repair but requiring improved performance in order to achieve the government’s 2050 carbon reduction target.

We must not forget that the 2050 Climate Change target is not some arbitrary political policy, but one based on the environmental challenge facing all of us. We need to play our part in slowing down the speed of climate change and adapting to the changing natural, social and economic environment.

The solar houses in Pembrokeshire are wonderful. But until we start building huge numbers of buildings with similar credentials, we are just celebrating a cottage industry rather than restructuring our urban environment for an uncertain future.The Conversation

John Grant is senior lecturer in natural and built environment at Sheffield Hallam University.

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