Not just 'woody weeds' - spreading shrubs have silver lining

June 1, 2011 By Bob Beale
Not just
Wattles encroaching onto former grazing land in the semi-arid rangelands of western NSW. Credit: UNSW

The global spread of native trees and shrubs into open grazing land and abandoned farms can bring unexpected environmental and economic benefits, a major new international study has found.

While many landholders have a negative view of these so-called "woody weeds" because they reduce grass cover, the study found new evidence that they also improve soil health and provide important habitat for native animals.

are likely to increase and become more prominent with rising concentrations of atmospheric carbon dioxide, says Associate Professor David Eldridge, who led the study published in the journal . The research team also involved scientists from Spain and the US.

" will probably result in even more encroachment of shrubs and trees than we have seen already," says Professor Eldridge, of the UNSW School of Biological, Earth and Environmental Sciences.

"This is seen as a problem by graziers because woody plants can hamper sheep mustering and reduce grass cover.

"But our findings demolish the view that encroachment equates with degradation.

"Landuses such as wildlife conservation, timber harvesting, ecotourism and will be the big winners under an environment of denser woody plants."

The researchers reviewed information in 244 published and unpublished scientific reports from around the world, revealing a far more complex and more positive picture.

They looked a wide range of factors linked to encroachment, including grass cover, available soil phosphorus, soil and above-ground carbon.

Surprisingly, perhaps, they found that increasing shrub density makes little difference to most of those attributes. Some of those that do change, however, hold out hope of significant environmental and economic benefits.

"Research has shown, for example, that dense stands of shrubs are substantial sinks for ," Professor Eldridge says.

Credits gained from large carbon sinks could provide financial benefits to rural communities under dedicated carbon-trading programs."

In Australia, large areas of semi-arid woodland are now occupied by native shrubs growing more densely than before European settlement. The study found that areas dominated by shrubs have less grass but healthier soils, with more soil carbon and nitrogen, and more above-ground plant material.

"The studies show that these shrubs provide habitat for many birds, insects and mammals, such as marsupial mice.

"Although dense shrubs can create problems for some pastoralists in drier areas of NSW, other landholders are encouraging the natural spread of shrubs and trees to restore degraded environments and improve soil health."

Explore further: Lands surface change on Alaska tundra creating longer, warmer summers in Arctic

Related Stories

Soil nutrition affects carbon sequestration in forests

December 13, 2006

On December 11, USDA Forest Service (FS) scientists from the FS Southern Research Station (SRS) unit in Research Triangle Park, NC, along with colleagues from Duke University, published two papers in The Proceedings of the ...

Emphasis on conifer forests places multiple species at risk

August 23, 2007

The traditional emphasis on dense, fast-growing, conifer-dominated forests in the Pacific Northwest raises questions about the health of dozens of animal species that depend on shrubs, herbs and broad-leaf trees, a new analysis ...

Energy crops impact environmental quality

April 4, 2010

Crop residues, perennial warm season grasses, and short-rotation woody crops are potential biomass sources for cellulosic ethanol production. While most research is focused on the conversion of cellulosic feeedstocks into ...

Recommended for you

Study shows sharks have personalities

May 27, 2016

For the first time a study led by researchers at Macquarie University has observed the presence of individual personality differences in Port Jackson sharks.

Automating DNA origami opens door to many new uses

May 27, 2016

Researchers can build complex, nanometer-scale structures of almost any shape and form, using strands of DNA. But these particles must be designed by hand, in a complex and laborious process.

Faster, more efficient CRISPR editing in mice

May 27, 2016

University of California, Berkeley scientists have developed a quicker and more efficient method to alter the genes of mice with CRISPR-Cas9, simplifying a procedure growing in popularity because of the ease of using the ...

Hawk moths have a second nose for evaluating flowers

May 27, 2016

Flowers without scent produce fewer seeds, although they are visited as often by pollinators as are flowers that do emit a scent. Scientists from the Max Planck Institute for Chemical Ecology in Jena, Germany, made this surprising ...

How sunflowers track the sun

May 27, 2016

Plants tell time. Not the way we do – for example, it's 3.40pm, time to pick up the kids. But like animals, plants can sense that winter is coming and it's time to drop leaves.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.