This photo was taken inside Idalia National Park, west of Blackall in Queensland, on 14th Nov 2009. There are no sheep or cattle in the park, only protected kangaroos. The netting enclosure shows the potential for both grass growth and carbon storage. Plants need to be allowed to grow if there is going to be a build up of carbon in Australian soils. Put simply, plants need to be able to photosynthesise if they are to transfer carbon from the atmosphere to the landscape.
Taking a systems approach
Most people who comment on carbon and greenhouse outcomes, usually leave out some of the accounting.
The broader community is not aware that, in many areas of Australia, kangaroos are negating the best efforts of rural producers to better manage the carbon cycle, and so achieve the outcomes society is relying on.
Kangaroos, like sheep and cattle, have the ability to degrade the landscape, which in turn leads to a drop in soil carbon levels. Furthermore, the presence of kangaroos leads to higher methane emissions per kg of production by ruminant animals (sheep and cattle).
If we want to maximise soil carbon, animals should be eating excess growth and not the first growth of plants. As an uncontrolled animal that goes through fences, the kangaroo is always going to be in the wrong place at the wrong time. By concentrating on fresh shoots, kangaroos often shut down more carbon flows than they actually consume. The Carbon Grazing principle highlights the need to allow plants to grow immediately following rain, if carbon flows from the atmosphere are to be maximised.
Research has discovered that kangaroos are even more selective than sheep in what they select to eat. In dry times, kangaroos are more restricted than ruminant animals in what they can successfully digest. This means they will just remove the dry leaf and leave behind the less digestible stem. Their need for and ability to select a more digestible diet, means the quality of the diet left for ruminant animals, especially cattle, is lower. The result is that sheep and cattle produce higher methane emissions per kg of production. This is because the cornerstone of reducing methane emissions by ruminant animals is to improve the digestibility of their diet. Improving diet quality is where a lot of research dollars are currently being directed. You can't blame the kangaroo for accumulating where the highest quality diet exists.
When grass is short, and kangaroos follow storms, they reduce the resilience of pastures by interfering with the replacement of energy reserves. This occurs because they keep removing the fresh new shoots.
One of the key strategies to reducing the impact of climate change is to increase the resilience of the landscape. It is resilient landscapes that are better equipped to absorb the changed circumstances that climate change brings, while fragile (degraded) landscapes collapse.
Article - further information on the carbon footprint of kangaroos.
Ongoing research to better understand kangaroos
Ten years ago, running wire enclosures and netting enclosures were constructed on commercial country. The purpose of the enclosures was to better understand the contribution of kangaroos to total grazing pressure and investigate suggestions that they may be responsible for inhibiting regeneration of the landscape.
The netting enclosures restricted both commercial animals and kangaroos. The running wire enclosures restricted commercial animals but not kangaroos.
Earlier work documented their impact of pasture production and regeneration phases, including seed production. Current work has focused on kangaroo contribution to methane outcomes going into dry times. It is dry times that require the greatest research effort as this is when methane emissions per kg of production grow exponentially.
The latest information supplied by these enclosures is that kangaroos are responsible for commercial livestock producing higher methane emissions, especially cattle. The following photos, all taken on the same day, on a cattle operation, highlight that kangaroos are selecting the dry leaf in preference to the lower digestible stem.
Above Photo - Commercial country grazed by kangaroos and cattle. In the background is a netting enclosure that cattle and kangaroos can not enter.
Above Photo - Inside the netting enclosure, showing potential dry leaf (which is more digestible than stems).
Above photo - Close up of dry leaf in the netting enclosure.
Above Photo - This photo is taken inside the running wire enclosure that kangaroos can enter but cattle can not. In the background is the netting enclosure that neither cattle or kangaroos can enter. The area between the two enclosures is grazed by both cattle and kangaroos.
Above Photo - These fencing materials form part of an individual rural producer's project to fence out kangaroos and protect the landscape (estimated cost $500K).
Above Photo - A previous attempt, using an electric wire, to reduce kangaroo grazing pressure on pastures.