The following article was written for us by Ashwal M. Gowda who is a Masters student from Bond University on the Gold Coast. Ashwal has been working with the Natura Pacific team this year to gain work experience in the filed of environmental consulting. His article is a fascinating insight into the world of the ghost crab, the importance of this species as a part of our beach ecosystems and the impacts of human activities on this precious little inhabitant of our coastlines.
Impacts of Recreational Activities on the Abundance and Distribution of Ghost Crabs in Sand Dune Habitats
There is increasing concern regarding the impacts of human activities, including recreational activities, on sandy beach environments. The ghost crab, Ocypode cordimanus is a widely distributed Australian species that is found on sandy beaches and dunes. Studies suggest that beaches that are exposed to more human interference and disturbance have significantly lower ghost crab abundances than beaches where these activities are sparser. The most plausible reason for this difference in abundance is that ghost crabs are highly vulnerable to being crushed by human trampling caused by recreational activities such as fishing, camping and driving off road vehicles on the beach.
Amongst coastal ecosystems, sandy beaches are the most intensively used by humans. Over the last few decades, impacts on sandy beach environments are escalating with greater intensity due to widespread growth and development, which is occurring at an alarming rate. These developments are largely driven by the exponential growth of human populations in coastal regions and have resulted in substantial alteration to the flora and fauna that are found in these regions. These alterations occur as a result of developmental activities such as shoreline armoring, and the construction of roads and buildings, which are threatening the coastal ecosystem by invading and destroying the sand dunes that serve as habitat to many species. However, infrastructure developments are not the only cause of sandy beach degradation. Leisure activities such as camping, fishing and driving off road vehicles on beaches are also causing impacts on this relatively fragile environment.
Ghost crabs typically inhabit the upper regions of sandy beaches by excavating burrows in sand dunes. There are many similar invertebrates that are present in these areas but because of their size and activity, ghost crabs are the most evident and hence are the main predators here. Ghost crabs are a vital part of the food chain in the coastal ecosystem as they help in transferring energy into different trophic levels, and can be considered a keystone species. They are the top invertebrate predator as well as being prey for vertebrate consumers in the sandy beach ecosystems. They spend their nights feeding and the days in their burrows and are especially susceptible to trampling and getting run over by off road vehicles being driven on beaches at night.
There have been many studies conducted on the correlation between human impacts on the environment and ghost crabs. Results from these studies show that there are fewer numbers of ghost crabs found in areas supporting human activities. These activities are usually recreational and include beach fishing, beach camping and the use of off road vehicles, resulting in the trampling or crushing of ghost crabs. Studies have also found that there were more ghost crab burrows found on beaches that did not permit vehicular activity and more ghost crabs to be found on non-urban beaches as compared to urban beaches. Similar research was also conducted on Brazilian beaches, which indicated the same results. This gives further testimony to the fact that recreational activities do indeed affect the abundance of ghost crabs.
The impacts of human activity on our natural environment are causing severe degradation to coastal regions in many parts of Australia, including the structure and function of our dune systems. This being said, of course eliminating human activities from sand beach ecosystems is not a realistic or achievable goal because these places are not only extremely popular with both residents and visitors, they also contribute significant benefits to our economy. However, by using the already available information to conduct more rigorous environmental investigations and implement sustainable tourism management practices, we could go a long way towards better protecting our sand dune ecosystems. Of course the attention of government agencies to this issue, and the implementation of measures to conserve the biodiversity of these ecosystems, will be paramount if these ecosystems are to continue to function into the future with their biodiversity intact.
https://en.wikipedia.org/wiki/Ocypode (Cropped version of File:Sand Crab (Ocypode pallidula).jpg. Sand Crab (Ocypode pallidula, Point Lookout, Queensland, Australia)
https://commons.wikimedia.org/wiki/File:111206_Ghost_crab_predation_Gnaraloo_Bay_Rookery.JPG (Photo courtesy of the Gnaraloo Turtle Conservation Program, Western Australia.)