Here at DCQ we use drones for lots of things but one of the main things we do is to use them to take lots of overlapping pictures of a site which computers can stitch together for form one image like grandma used to do when making a quilt. Now when you have this image you can “look” at it in many different ways and in many different spectrums to highlight different things. It allows us to extract information on key parts; say how many prickly trees are in a paddock, or in this case, how much green grass is in an area. And if you compare it over time you start to get trends. The image below is from a trial site commenced in 2018 and which has been monitored monthly since then. The area had hectare areas fenced to allow for full exclusion, exclusion of domestic stock and no exclusion.
The images we taken a month apart in January and February this year as the rain really started and then well into the growing season. Firstly it showed that stock has been heavily grazing the no exclusion sites and that after 4 years of scattered and light rain, the full exclusion area was suffering from some pasture decline, but importantly it showed an early and fast response due to the grazing by kangaroos. If this is where the story ended, conclusions would be obvious – there cattle are heavily impacting there area and the kangaroos, without the stock are actually benefitting there area. A month later and following good rain, the story is very different, in fact all areas are performing the same. It shows the incredible growth capacity of the native perennial pastures and their ability to respond and recover and so the story gets more complicated. If you just looked at this second image you would say that cattle, and kangaroos have no impact, but this is just because the growth rates exceed the grazing rates at this time.
We will continue to monitor the sites throughout what is turning out to be a great season to see the changes but the data to date confirms some well known things we sometime forget. Our native pastures in the region benefit from disturbance (grazing and fire) and shouldn’t be left too long or they will start to naturally decline, and pastures which are not overgrazing can respond amazingly quickly.
We will continue to monitor the sites to deal with the most vexing of the questions the trial was set up to sort out…just what is the grazing impact of cattle vs kangaroos.