The power of Dragons and Damsels – Issue #68

Hello Explorer,

We continuously hear and read about the effects of disturbances, invasive species and pollution on environments, habitats, and ecological processes. The question that then comes up is how can we easily, simply, and quickly determine the health of a habitat, ecosystem, or environment? One of the best ways are using a Biological Index of Ecological indicators. A biological index is a group or collection of species that range in how environmental changes, disturbances, or pollutants effect each of the species. Usually, it is best to utilize a group of related species, such as a single taxonomic classification, for instance Birds in the Class Aves (all birds), or an order like in the case of ODONATA (Dragonflies and damselflies), or even a family like in the case of Ants (in the Order HYMENOPTERA and the Family Formicidae)

Birds are often used as a biotic index to determine the health or environmental changes within an ecosystem. A good example of how birds are used as an index of ecosystem change is the dune forest restorations in Kwa-Zulu Natal. Where they use the present bird community to determine how well a part of dune forest has been restored to its natural state.

Another very good biotic index are ants, as they are abundant, easily sampled and very connected to the functions of an ecosystem. Specialist species only occur in undisturbed areas, whereas pioneer species, that can occupy and utilize any habitat, will occur in any habitat irrespective of the level of disturbances. Freshwater is one of the most important natural resources there is, and unfortunately also the one that is most easily degraded and polluted. A major challenge is how we measure the water quality and the integrity of the ecosystems surrounding the waterbody, whether it’s a river or lake. Biotic indices are often used to determine the health of ecosystems.

For aquatic systems such as streams, rivers and lakes or dams, the invertebrates that are present can be used as a biotic index to determine the health of the waterbody. Many of the invertebrates, however, must be sampled by getting into the water and catching them by one way or another. Here in the Lowveld, however, that is something that should be avoided at all costs. The hippos and crocodiles in the Lowveld are big and very sneaky, so getting into the water is not a good idea at all!

The Dragonfly Biotic Index (DBI) of South Africa focusses on the Dragonflies and Damselflies (ODONATA) that are present around the waterbody. Each species of ODONATA in South Africa has been given a DBI rank ranging from zero to nine. The rank is based on the geographical distribution of the species, it’s habitat sensitivity (sensitivity in changes to the habitat through disturbances or pollutants alike), and its threatened or RED list threat status.

Species with a wide distribution range, that is least affected by changes, disturbances or pollutants in its environment and not threatened by any means, have a ranking of zero. Species that have a restricted range, are very sensitive to changes in the environment, whether pollutants or minor disturbances, and are listed as threatened, endangered, or critically endangered have a ranking of 9. Thus, water bodies of high water quality with no disturbances will likely host species with higher rankings.

The DBI of a waterbody can be determined by first identifying the ODONATA species that are present. The DBI rankings of the respective species that are present are then summed, and divided by the total number of species present at the waterbody.

The DBI is an easy and simple Biological index to use for anybody. Most dragonfly and damselfly species can be identified through simple field observations without the need to capture the specimens. A very good resource for anyone interested in ODONATA or that want to use the DBI index for themselves is the book “A field guide to the Dragonflies and Damselflies of South Africa” by Warwick and Michèle Tarboton.

If you would like to read more about the DBI index there is a very good article written by Samaika and Samways in 2012.

Have you grown bored with Bird Watching? You should truly consider watching Dragonflies and Damselflies then, as you already know how to use a field guide and most likely have the required equipment! All you need is a good field guide like the one I linked above and a pair of binoculars to start!

Did you know that invertebrates can be such good bioindicators of the environment? What other invertebrates do you think can be used as a biological index to determine ecosystem health? Why do you say that this group of invertebrates could be a good biological index?

If you would like to send me a message with your answers, feel free to do so on Instagram @abugmanslife or via email to [email protected].

Weekly Top Shot: Red-veined Dropwing