Grasslands are areas with few natural trees or shrubs and
are dominated be grasses as the name suggests.
These are some of the world’s most iconic landscapes – think of the
plains of the Serengeti in Africa, the savannas of North America and the
steppes of Europe and Asia.
Here on the Plains grasslands are a vital part of our
livestock business supporting significant cattle production. An important part of our business management
is matching the needs of our livestock with pasture availability. This ensures that the land is not overgrazed
and the welfare of the livestock is maintained.
A particular issue we have with the grasslands on Anna
Plains is the encroachment of Mealeuca (paperbark) species on the grasslands of
Anna Plains. Photo monitoring from
station management together with aerial photos and satellite images shows the
encroachment of paperbark.
These trees obviously reduce pasture availability to
livestock and they reduce the abundance of foraging ground for migratory
shorebirds. In addition they also
provide refuge for predators such as birds of prey and feral cats.
The encroachment of trees onto grasslands is not a situation
unique to this part of the world.
Reports of trees encroaching onto grasslands have been made in Africa
and North America.
The reasons for the tree encroachment are on grasslands are
not fully understood. One reason could
be increasing levels of carbon dioxide in the atmosphere which favour the
growth of trees as opposed to grasses.
Most of the grasses in this part of the world use the C3
pathway for photosynthesis as opposed to the C4 pathway which many trees have
evolved to use. C4 plants are more
efficient than C3 plants and are well adapted to high temperatures and moist
environments, both features of our grasslands here on the Plains, particularly
in the wet season.
The concentration of carbon dioxide in the atmosphere will
continue to increase. If the higher
levels of carbon dioxide are a factor in the spread of trees on the grassland
then we will have to learn to deal with it.
Potential management solutions include the use of fire to control tree
growth and the use of grazing animals to knock back the trees. The use of herbicides could also be
considered in some areas although the scale of the rangelands means this
solution would be impractical.
FURTHER READING
Grasslands in a
changing world. Drovers Cattle
Network. http://www.cattlenetwork.com/expert-columns/?author=Joseph+Craine&aid=213203031
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