Mimosa pigra (mimosa) is an invasive shrub that is fast invading the wetland grasslands of the Kafue Flats, a vast wetland complex in central Zambia, negatively affecting the habitat for thousands of Wattled Cranes and large herds of Kafue Lechwe. The ICF/EWT Partnership has received a generous grant from the Segre Foundation to remove over 90% of the infestation of this invasive species from the Kafue Flats over the next 3 years. This is an ambitious project that not only will restore the floodplain grasslands of the Kafue Flats for cranes and lechwes, but will benefit the local communities by way of gainful employment opportunities they will receive over the next 3 years or more during the course of the project.
Thus, we have targeted to start the invasive removal project in July this year once we have complied with Zambian regulations of undertaking such a huge project. But in order to plan our next course of action – i.e. to set our control strategy, a detailed map showing the distribution of Mimosa is highly needed. We partnered with the Kafue River Trust – to map the Mimosa across the entire Kafue Flats so that we have a baseline from which we can compare at the end of the project. To do this, we needed to carry out ground truthing work where we collected location data of a sample Mimosa infested area in Lochinvar and Blue Lagoon National Parks and then use this to map the Mimosa infestation across the entire Kafue Flats. Since the Kafue Flats are currently flooded, it was impossible to do this from the ground and so we had to do this from the air.
On the 18th of May 2017, we conducted a reconnaissance flight covering the Blue Lagoon and Lochinvar National Parks and parts of the Kafue Flats Game Management Area. Not only were we to look for Mimosa infested areas, we also set out to spot large herds of Kafue Lechwe and flocks of Wattled Cranes and other interesting landscape features. One of the key objectives of conducting the flight was also to have a visual impression of the how much mimosa has expanded compared to previous years.
From the aerial survey, it was evident that the extent of Mimosa in Lochinvar and Blue Lagoon National Parks has expanded compared to previous observations. The worse is the marked increase of Mimosa infestation in the Blue Lagoon National Park. In 2009, it was reported that the Mimosa infestation at Blue Lagoon occupied an area of less than a hectare in the floodplain grasslands around the Shamikobo area in the Park. Our flight over that same area suggests that the Mimosa has expanded and is occupying an area far more than 2ha (see photo 1). In the Lochinvar National park, the areas that were previously controlled in 2007 – 2009 have largely been reinvaded but other areas still remain free of Mimosa and have largely been restored (See photo 2). New areas that were free of Mimosa are now being overtaken too.
We further searched for Wattled Cranes and flew over an area we flew in 2015 where we saw a flock of over 400 Wattled Cranes. Unfortunately, the cranes were not present there or anywhere near that area. What was highly noticeable was that the water level was much higher during this current survey than in 2015. It is therefore highly likely that the cranes are located in a much shallower area on the Kafue Flats or possibly migrated to other wetlands in Zambia where the conditions are favourable for them. But we saw 3 pairs of cranes (See photo 3) – possibly beginning to nest – on the edges of the floodplain and a small flock of about 40 individuals.
Large herds of the Kafue Lechwe (See photo 4) were also seen. Kafue Lechwe is a semi aquatic antelope that is endemic to the Kafue Flats and is often found in association with wattled cranes here. As with the cranes, the habitat for the lechwe is also impacted by the mimosa.
Overall, the aerial reconnaissance flight was a huge success. Once the data is compiled and analyses done, we will have a map that gives us the current extents of the mimosa and one that we will use to set the strategy for our control project. Furthermore, this map will be our baseline on which we can base how effective our control intervention on the Kafue Flats would have been.
Article by Griffin Shanungu