Any homeowner can attest that one of the biggest challenges they face yearly is dealing with unsightly weeds on their property.  Treating for weeds is a never ending process.  At the beginning of each spring season a first round of treatment is needed.  Follow up treatments are usually needed to keep lawns weed free throughout the spring, summer, and early fall.  Even then there are persistent patches that will sprout up overnight that need to be dealt with by hand.  Now imagine the magnitude of dealing with invasive weeds in a massive national park.  Kakadu National Park in Australia is facing just such a problem.

Kakadu National Park covers around 20,000 sq kilometers in the Top End of Australia.  For more than 65,000 years it has been the home of Australian Aboriginal people and has been listed as a World Heritage site for both it’s cultural and ecological impacts.  In the 1960s, before it was made into a national park, Kakadu was used as grazing grounds for livestock like buffalo and cows.  To be able to cheaply and easily feed the grazing cattle para grass (also known as buffalo grass) was introduced to the region.  As a park, there are no longer grazing herds in Kakadu, but the grasses have remained.  Para grass is not a native plant to the area and has thus become and invasive weed causing damage to the natural wildlife and fauna of Kakadu.

One way park rangers have been noticing a shift in the natural ecosystem of Kakadu has been in the decline of magpie geese.  Magpie geese would normally make nests in the grassy wetlands of Kakadu Park.  These wetland nests would provide them shelter and a food source.  However, because there is more para grass than the natural grass in the area, the geese have moved on.  Dr Micheal Douglas, a board member of Kakadu National Park, professor at the University of Western Australia, and leader of the National Environmental Science Program (NEST) Northern Australian Environmental Resources Hub said, “Para grass has proven to be a really aggressive and fast-growing weed, and so it spread throughout the park, and where it moves into these flood plain areas, it completely displaces the native plants and really what you’re left with is a one- or two-metre high lawn.  Effectively, it’s a monoculture of this weed, completely devoid of native plants, and that comes at a huge cost to the native plants that would provide nesting sites and feeding sites for these magpie geese, for other ducks and wildlife including turtles.”

The problem is, how do you even begin to tackle a weed infestation over such a vast area?  To do this, a partnership between the Commonwealth Scientific and Industrial Research Organization (CSIRO) and NEST, as well as Parks Australia, and Microsoft have formed a program called Healthy Country.  CSIRO research scientist Justin Perry said, “Weeds are terrible things to manage, they always come back, they’re at such large scales.  Kakadu National Park, it’s two million hectares, these wetlands are enormous, some of the biggest wetlands in the world. When you get an invasive weed like para grass, it’s not a trivial problem.”  He went on to say just how overwhelming it was to look out across a stretch of the park and wonder how they could even make a dent in the weed problem.  So that is when they turned to drones to give the Healthy Country mission a boost.

The first step in dealing with the weed infestation was to identify what areas of the park in fact need to be treated, without compromising any healthy wetlands.  Perry said, “When you’re standing at ground level, you’re looking out over thousands of hectares of weed, and you stand and go: ‘What am I doing? What can I actually achieve here?”  He knew the best method would be to get up in the air.  But using a plane or helicopter would be too expensive, therefore only allowing them to get a birds eye view one time.  The team needed something inexpensive that they could use on a regular basis to track the progression of the para grass.  They decided to purchase an off the shelf DJI Mavic drone.

The DJI Mavic drones are some of the most popular drones in the world.  They deliver superior results at an affordable price and are easy to use.  Healthy Country’s aim was to send the drones up in the air to identify sections of wetlands to be treated, monitor the treatment results, and collect data on how many magpie geese were in the region.  They began by designating a 90 hectare trial site, flying the drones along a pre-programmed route 60 meters above ground.  All the data collected was put into a Power computer to be analyzed.  For rangers like Perry, who has spent years trying to monitor para grass, this has saved him massive amounts of time and energy.  He said, “We’ve gone out and flown the drone, collected some information, it’s then been provided back to the rangers the next time we went out there. And so you can look at it, and go oh jeez, we actually were successful.  And that’s been an amazing motivator, because weed management is thankless, it’s a thankless task.  But the rangers don’t have to think about that, they just have to go out there and press the button.  The drone comes up, it flies, it does its route, it comes back in and it lands.  If it runs out of batteries, it comes back and lands, they put a new one in and it goes and flies it again and finishes off the transect.”

The results were better than expected Dr. Douglas said.  “We’ve removed para grass from that area, and the results have been spectacular,” Douglas said.  “When we first started doing this project, that area was 100% para grass and we were able to count just 50 magpies. Nine months later, the area is teaming with native plants and we recorded more than 1,800 magpie geese.”  This does not mean that there was suddenly a magpie geese baby boom.  Rather the geese now have more options as to where they can make there nests and are returning to a nesting ground that had historically been ideal, before the para grass infestation.  These same ramifications will effect other natural plant life and wild animals in Kakadu Park.

And since Healthy Country is using drones instead of planes they will be able to carry on this mission throughout the year.  Weed management needs to be maintained on a continual basis, and using the drones will allow the park rangers to do just that.  They can fly a drone out weekly or even daily to see where patches of para grass is returning or has yet to be treated.  By keeping up this persistent visual tracking Healthy Country may be able to fully purge Kakadu Park of all para grass.  The drones will also give the rangers a significant tool for tracking and counting the parks wildlife year round, providing them with even further data as to the park’s overall health. 

For now, the drones will be used just to maintain a visual record of the process.  But, Dr. Douglas pointed out that because of the initial success the team has had with the drones they will start looking into other ways to use them.  One such way they may start utilizing the drones would involve finding a way to use them to spray the weed treatments as opposed to doing it by plane or truck.  This would mean having to purchase a drone system specifically designed to carry and spray chemicals, which is why this is just an idea for the future for now.

Previous Drone News: