The overuse of fertilisers can have detrimental effects on native flora. The most common elements included in agricultural fertilisers that can be harmful to the Australian landscape are nitrogen and phosphorus. Australia’s plants are evolved to a landscape that is low in phosphorus, so too much of it can be toxic for many plants. In other parts of the world such as the Netherlands, there are strict regulations on fertiliser use in order to mitigate these pressures.
In high rainfall areas, especially those with sandy soils, there is a high risk of the fertilisers being leached into the ground water. The build-up of phosphorus in these systems can contribute to algal bloom development. This is damaging for aquatic species, mainly because the presence of the algae inhibits sunlight reaching the other photosynthetic species below. This can decrease biodiversity in rivers and lakes for photosynthetic life forms as well as those that depend on those plants for food.
The build-up of ammonium nitrates in the soil can contribute to soil acidification. This can lead to the die back of any species that is not evolved to cope with acidic soils. This is mainly a problem for agricultural lands and can be a major factor in paddock tree die back and lack of regeneration.
The Netherlands, which has a large agricultural sector being the second largest exporter of agricultural products in the world, has a system of accounting for all nitrogen that goes in and out of the system. If too much nitrogen is lost, taxes apply. The Dutch Government has also developed an online computer game called NitroGenius to educate people on the problems of nitrogen pollution.
Phosphorus is a scarce resource throughout the world so it does not make sense to waste it in polluting our ecosystems. Solutions for this problem include the consumption of less meat and more plant-based foods that are more efficient users of phosphorus, and the use of animal excreta as fertilisers.
Another solution to this problem may the uptake of organic farming. Organic farming involves only using natural fertilisers like animal manures and worm castings in place of synthetic fertilisers. It has been shown that there is usually less nutrient run-off and leaching through organic farming practices.
Lessening the pressure on biodiversity through the proper management of fertilisers is important in Australia due to the fragmentation of our natural systems. This is essential for the preservation of paddock trees – an integral aspect of Australia’s declining biodiversity.
Ellie Stanley – Bachelor of Science, Australian National University