Biodiversity in wetlands
Whatever the main objective for a wetland is, it is always possible to add measures to improve the conditions for flora and fauna. The most critical section is the transition zone between water and land (the littoral zone). It is here the accessibility to the water is determined and this is where there might be shelter and food for many species.
How the biological diversity of species numbers and species composition develop in our wetlands depends on many factors, of course. But three factors can be mentioned which have more effect than you might think.
Variation of the water level Natural wetlands in Northern Europe often have lower water level during summer and winter than during spring and autumn. Lowered water levels expose the littoral zone where some water plants dry out. New plants establish which in turn can be flooded and die, when the water level increases. This natural stress situation along the beaches gives many plant species compete for space along the littoral zone.
These natural disturbances create habitats that become valuable for a number of animal species. A stable water level often leads to monocultures where one or few species expand at the expense of all others. Disturbance along the littoral zone can also be achieved by grazing or mowing. It is the disturbances that lay the foundation for increased diversity.
When you understand this relation, it is a logical conclusion that gentle slopes and long irregular littoral zones provide much larger potential for biodiversity than straight littoral zones with steep slopes.
Access to sunlight
Sunlight produces heat in the air and water and in our latitudes, this warming is essential for achieving high biological activity. In southern latitudes sunlight may result in too high water temperature. In this case shading may keep the water temperature tolerable for the aquatic life. In the north it is usually the other way around. Shading leads to sub-optimal water temperatures and the development of amphibians and insects in the water is delayed. But the sunlight also consists of photons utilized by the plants in the photosynthesis process, which is our planet's key to life. Together with the water.
When the inflowing water to a wetland is turbid the water depth is a critical factor for biodiversity. Without plants no food for water fauna, which is the foundation of amphibians and birds' diet. Additional shading by trees in those circumstances is obviously completely devastating.
Even the best habitat is not habitable if there is no shelter or protection. For animals, it means they should have access to protection e.g. between rocks under or above the water and they need to find suitable places to lay their eggs. Stones, sand, branches, dead wood, short and tall grass, an island, a bridge, a shallow area across the wetland: Everything could be of interest. Unfortunately we do not always know exactly what our little friends prefer. Therefore, the very best we can do for them: Do not think that we know, but create as many options as possible: Variety, variety!
|© Peter Feuerbach|