Freshwater ecosystems fall into some of the most threatened ecosystems due to pollution, invasive alien plants, and high volumes of water abstraction (taking water from any source). The freshwater ecosystems are also one of the most important ecosystems for so many different species whether it’s to provide a home for numerous species such as crocodiles, fish, frogs, or even the tiniest larvae of a Dragonfly. It is also what quenches the thirst for many different animals’ survival. These are just a handful of the many reasons why it is so important to protect, for us at Londolozi, the Sand River.
Recently, one of the Sabi Sands Private Game Reserve’s ecologists came to assess the health of the portion of the Sand River that flows through Londolozi. His approach was to test water samples for any contaminants/pollution and the freshwater ecosystem quality, in terms of species diversity along the Sand River at different points.
The first place to test was at one of the rocky crossing points in the Sand River, some of you that may know where I am talking about, ‘Taylor’s crossing’. This was the perfect place to test as it has reeds, rocks, and sand creating a perfect freshwater ecosystem.
We started by testing the water visibility by using a clear tube with a dark movable circle that you push back until you can not see it. The clearer the water is the higher the quality of the water is. The visibility was good for this point in the Sand River. He told me that as you go further downstream in the river the water quality increases due to the filtration from the sand and less turbulent waters will have less suspended substrate held in it.
The next test was to collect many different species samples from the different parts of the river, he used a net to collect larvae and nymphs from the flowing water, between the reeds, and in the sand. We then had to use a magnifying glass to identify the different species that we had collected. Each species has a taxonomical number, the more sensitive the species are to their environment the higher their number will be. I will try to not get too complicated, but basically, you would want more sensitive species to get a higher score which will mean the river ecosystem is healthy as sensitive species have managed to survive there.
I noticed while calculating the species numbers that dragonflies have a high score and are extremely sensitive to changes in their environment therefore would be a good indicator species for a healthy ecosystem. This is helpful as the larval and nymphal stages of a dragonfly’s development are found in water.
This sparked an idea in my head. What if I try and identify all the different Dragonflies we get here at Londolozi and count them to see if there is an increase or decline in their population indicating if the river’s ecosystem is positively or negatively changing? This means that every year when it is summer we set out with a dragonfly identity book and sit along the Sand River and count as many different species of Dragonflies as possible.
With all the rangers willing to help, by either taking a photo of a dragonfly that they see out there or by identifying them so we can record it. It is going to be a difficult task to get the photos as dragonflies are constantly on the move and do not stay still for long.
However, I am in the process of making an ID sheet with all the common Dragonflies that we get here to help us out.
Not only is it a way to test the health of the freshwater ecosystems at Londolozi but it’s also a way to learn more about these fascinating insects. I mean just a quick few facts on Dragonflies can be draw-dropping. For example:
Most of the Dragonflies we can see here are migratory. One, in particular, The Wandering Glider, has the longest migration for any insect. It migrates over 16 000 kilometres (10 000 miles) over the course of four generations throughout the year; a truly remarkable migration!
Dragonflies have a near 360-degree vision which gives them the ability to pinpoint a single insect in a swarm and manage to stalk straight into the swarm without colliding with other insects.
They can also move all four of their wings independently making them extremely agile in the air. Giving them an almost 95 per cent success rate when hunting, making them phenomenal predators.
I could go on and on about how exceptional dragonflies are but most importantly I would like to try to turn this idea into The Dragonfly Project and will hopefully get enough data to come up with an update to share with you all in the years to come.