Drivers of Loss and Change to Wetland Ecosystems

Wetlands are an expression of the hydrological cycle; water fixed in global cycles. As biological functioning systems they are crucial to river catchment ecology by absorbing additional excess nutrients and pollutants prior to reaching other water bodies. The exponential growth of human development has coincided with the decline of global wetlands. This loss of wetlands and the reduction of integrity of remaining wetlands has been more swift than any other habitat globally that it is a biome that requires significant conservation.

What are the ways human development has contributed to the loss and fragmentation of wetlands?

Human settlements have always been closely aligned next to or near water bodies as a source of water for consumption and agriculture. With growth there has been an early history use for wetlands as a dumping ground, quarry or animal stockage and alterations for human recreation activities such as marinas/boating. The facilitation of human movement and activities around wetlands has subsequently contributed to changes in vegetation structure and composition, wetland hydrology, water and soil pollution and disrupting wildlife activity.

If we think of wetlands as an important part of a watershed that is part of the wider regional catchment, we can imagine the consequences where all water run-off from domestic, agricultural and industrial activities can end up in our local water bodies, including wetlands. This problem is magnified with the increase of run-off from hard surface areas, roads, rooftops and drains due to urban sprawl, that create a direct path towards local water bodies rather than infiltrating through the soil stratum where pollutants are filtered by vegetation.

Many wetlands have been drained and converted for industry, mining and agriculture. The implications from actions such as drainage, dredging, groundwater withdrawal and diverting or channelling streams and other forms of hydrologic alteration can affect soil saturation and inundation of flooding events. Changes also impact the quality of water discharged into wetlands increasing water temperature, pH, salinity and other toxic pollutants such as heavy metals. Compounds can enter wetlands through dry and wet atmospheric deposition. These are pollutants such as nitrous oxides, sulphurous oxides, heavy metals, volatilised pesticides and hydrocarbons discharged by industry and agricultural activities into the atmosphere. Gases can be absorbed by water or settle in sediments and diffuse throughout the system affecting aquatic and terrestrial organisms.

So far direct drivers to wetland loss or damage have been identified but there are also indirect drivers, most notably climate change. Climate change is expected to exacerbate the loss of wetlands through altered hydrological cycles (which will impact vegetation structure and composition) and increase the incidence of vector-borne and water borne diseases in many regions. There is also a disconnect as to how wetlands are used which are not always in agreement. For example land developers, engineers, scientists or a bird watcher will consider wetlands functions and values in different ways. These are some of the many pressures that are needed to be overcome if we hope to conserve what remains and manage wetlands in a sustainable manner.

 

photo credit: <a href="http://www.flickr.com/photos/angelslens/145825394/">lindley ashline [MOVED to lindley ♫]</a> via <a href="http://photopin.com">photopin</a> <a href="http://creativecommons.org/licenses/by-nc/2.0/">cc</a>