Natural Resources Protective Association: Protecting the marine environment since 1977

The Importance of Wetlands

Wetlands play an essential part in the regulation of river flow, they filter pollutants and fertilizers, they are spawning zones for some species of fish (pike in particular). They also provide a habitat for plants, insects, batrachians and birds…

The present valleys and river beds were formed in the aftermath of the last glacial periods (erosion, deposits of sand and gravel), followed by a return to the present climate (deposits of fine organic or mineral alluvial silt and ongoing erosion). Different types of features can be distinguished : from the river bed carved out of the rock to alluvial valleys formed from a succession of deposits of gravel, fine sand and peat.

The expanse of groundwater in these deposits when they are well developed can constitute a large reserve which absorbs the variations of water flow. Alluvial deposits act rather like sponges which absorb surplus water before releasing it later. In these alluvial areas part of the water follows the course of the river: this drainage can represent a large volume. This water has been filtered, has a more constant temperature and constitutes a reserve of good quality water.

When the flow of water from the river basin has to cross these alluvial formations before joining rivers significant quantities of nitrates or pesticides contained in the water are eliminated by the action of bacteria trapped in the soil or by the vegetation.

These two functions – regulation of flow and retention of diffused pollutants from the river basin –combined with the positive effects on the fauna such as providing a specific habitat for fish (a safe area for spawning for some species and pike in particular spawn in flooded grasslands) and bird life make these areas very important ecological zones.

In traditional landscapes these wetlands have specific features: wet grasslands, rushes, willows, etc. but in some regions the systematic drainage of this water-logged soil has resulted in the disappearance of these buffer zones. Even worse corn culture which leaves the earth laid bare for long periods, and which needs large quantities of fertilizers and pesticides appears to be disastrous for rivers downstream: sudden rises in water level, low water levels, poor water quality. Sand and gravel extraction in large alluvial valleys has also transformed the landscape. The consequences of these industries are often negative : floodwater no longer spreads out naturally but flows rapidly into rivers which increases the rise in water level. This water is loaded with organic and mineral material causing erosion of the river basin and alluvial silt is deposited in the river bed.

Wetlands which are vital to the balance of rivers and crucial for the diversity of animal and vegetable species can only be preserved through political resolve. They should not be merely abandoned but properly managed like other areas. Agricultural and forestry activities cannot be profitable within the structure of current policies, consequently owners and those working the land must be helped within the framework of landscape and river basin management. The flow and quality of rivers will depend on this action.

This article was copied from the E-zine