Ecology of coastal dune fauna

Abstract

The distinguishing feature of coastal dunes is their connection to the shore. This maritime influence results in most coastal dunefields exhibiting a marked shore-normal gradient of decreasing physical stress and increasing complexity and vegetation cover landwards. Physical stresses include sand movement, salt spray, temperature variability, wind and disturbances such as storms. Increasing vegetation cover, often coupled to succession, mediates physical stress, creates stable microenvironments and is responsible for a general increase in habitat complexity landwards. Fauna respond to this gradient in a number of ways. Crustaceans of marine origin decrease in abundance landwards. Many of the special adaptations, which equip fauna for psammophilic lifestyles and allow them to cope with salt spray and temperature extremes, are only encountered near the beach. Insects, vertebrates and interstitial fauna increase in abundance landwards as vegetation cover, height and diversity increase, soil develops and greater stability is attained. Biological interactions and impacts of fauna on vegetation via grazing, seed dispersal and disturbance also increase landwards. There may be a shift from primarily r-strategist species near the beach to k-strategists inland and birds may replace small mammals as vegetation height increases. Coastal dune fauna differs from that of deserts in being more diverse and having a well developed interstitial component. Furthermore, coastal dune inhabitants are less specialised to cope with physical extremes and are seldom unique or endemic to these systems. However, this fauna has received considerably less attention than that of desert dunes and much research is warranted on subjects such as adaptations to sand movement and salt spray, endemism, trophic relations and exchanges with adjacent systems. Wind is the major factor impinging on these dune ecosystems.