Dragonflies as potential indicators for wetland restoration progress
Habitat loss is one of the main causes of biodiversity loss. The human population continues to grow, along with our increasing demands. However, in the landscape mosaic full of degraded and destroyed habitats, where should the species, whose habitat we have taken for ourselves, seek refuge? For these species, only the protection of the current natural habitats is no longer enough and it is crucial to restore the habitats that we have disturbed or destroyed. This is the goal of restoration ecology (Jones et al., 2018).
Ecological restorations are becoming an increasingly popular topic. For example, the period between 2021 and 2030 is referred to as the Decade on Ecosystem Restoration (UN General Assembly, 2019). Nevertheless, it is no secret that restored habitats usually do not reach the quality they had before they were destroyed (Jones et al., 2018). One of the reasons for this might be the difference between human and animal perceptions of habitat quality. Additionally, we often struggle to fully restore ecosystem structures and ecosystem functions to the level they had before destruction. There are studies that indicate that even after decades, certain ecosystem structures in restored habitats, such as plant or macroinvertebrates communities, didn’t reach the reference values (Moreno-Mateos et al., 2012).
In particular, the problem arises when animals prefer restored habitats over natural ones, even though they have lower fitness and higher mortality in the restored habitats. At this point, restoration inadvertently creates ecological traps. Ecological traps are habitats, whose quality is low, but animals willingly choose them and prefer them. This differs from sinks, which also have low quality, but animals avoid them (Battin, 2004).
Animals choose their habitats based on signals and cues they have used for thousand of years. However anthropogenically induced environmental changes have occurred in such a short evolutionary time, that organisms can not adapt to these changes. These changes can confuse organisms, leading them to choose the wrong habitat, despite the fact, that they are using verified cues (Hale et Swearer, 2017). Robertson et al. (2013) found that ecological restorations are on third place among reasons why ecological traps occur. And that’s a significant problem, because ecosystem restoration is intended to benefit organisms and ecosystems, but it shows that the effect can be opposite.
Dragonflies have an interesting life cycle with imagoes being terrestrial and larvae aquatic. The mother selects a site for oviposition primarily based on visual perception. She uses proxy visuals cues, such as vegetation and polarized light (Wildermuth, 1994). The life of her offspring depends on her choice, despite the fact, that she doesn’t have the opportunity to test the site’s true quality. The mother cannot feel the correctness of her decision. This fact increases the chance of choosing an unsuitable habitat for her offspring and leads them into an ecological trap.
Dragonflies are often referred to as indicators of ecosystem health, because they reflect the condition of the ecosystem through their performance. In lower-quality habitats, dragonflies may exhibit lower fat content, smaller body size, weaker immunity, or higher mortality rates (Mikolajewski et al., 2015; Stoks et Cordóba-Aguilar, 2012). These factors make dragonflies potentially good indicators for wetland restoration progress and detecting ecological traps.
In conclusion, ecological restoration is a powerful tool, but it must be conducted effectively, ensuring that restored habitats truly provide sufficient resources for organisms. Monitoring of restored sites is crucial to verify the success of ecological restoration, and dragonflies could potentially serve as indicators. The aim of my future research will be to determine whether restored habitats can act as ecological traps for dragonflies. I also aim to verify whether dragonflies can assist in detecting ecological traps and serve as indicators of the success of ecological restoration.
The integration of knowledge from landscape ecology and environmental sciences is essential for improving the effectiveness of restoration and developing restoration techniques that are ecologically, economically, and socially appropriate. We need to work together for greener future.
References:
Battin J., 2004: When Good Animals Love Bad Habitats: Ecological Traps and the Conservation of Animal Populations. Conservation Biology, 18 (6): 1482–1491.
Hale R., Swearer S. E., 2017: When good animals love bad restored habitats: how maladaptive habitat selection can constrain restoration. Journal of Applied Ecology, 54 (5): 1478–1486.
Jones H. P., Jones P. C., Barbier E. B., Blackburn R. C., Benayas J. M. R., Holl K. D., McCrackin M., Meli P., Montoya D., Mateos D. M., 2018: Restoration and repair of Earth’s damaged ecosystems. Proceedings of the Royal Society B: Biological Sciences, 285: 20172577.
Mikolajewski D. J., Conrad A., Joop G., 2015: Behaviour and body size: plasticity and genotypic diversity in larval Ischnura elegans as a response to predators (Odonata: Coenagrionidae). International Journal of Odonatology, 18 (1): 31–44.
Moreno-Mateos D., Power M. E., Comín F. A., Yockteng R., 2012: Structural and Fuctional Loss in Restored Wetland Ecosystems. PLoS Biology, 10: e1001247.
Robertson B. A., Rehage J. S., Sih A., 2013: Ecological novelty and the emergence of evolutionary traps. Trends in ecology & evolution, 28 (9): 552–560.
Stoks R., Cordóba-Aguilar A., 2012: Evolutionary Ecology of Odonata: A Complex Life Cycle Perspective. Annual Review of Entomology, 57: 249–265.
UN General Assembly, 2019: United Nations Decade on Ecosystem Restoration (2021–2030): resolution / adopted by the General Assembly. A/RES/73/284.
Wildermuth H., 1994: Habitatselektion bei Libellen. Advances in odonatology, 6 (1): 223–257.
