Issue 13: Modification of ecosystems or ecotones, including community structure and/or species composition

Ecological systems play a fundamental role in supporting life on Earth at all hierarchical scales. They are essential in global material cycles like the carbon and water cycles. Ecosystems produce renewable resources (food, fibre, timber, etc.) and ecological services. For example, fish are produced by a marine food web of plants, animals and microorganisms. Fish are part of the ecological system in which they are produced, and the interactions that produce and sustain fish are inherently complex. Ecological services are also generated by ecosystems. These include:

· maintenance of the composition of the atmosphere

· amelioration of climate variability

· flood control and drinking water supply

· waste assimilation

· nutrient recycling

· soil generation

· crop pollination

· pest regulation

· food provision

· biodiversity maintenance

· and also maintenance of the scenery of the landscape, recreational sites, aesthetic and amenity values

Natural systems at genetic, species, population and ecosystem levels all contribute in maintaining these functions and services.

The increase of populations and economic activities in freshwater and coastal areas is leading to loss and modification of ecosystems. For example, excavation, oil and gas exploration and exploitation, mining, such as sand and aggregate extraction, the building of ports and marinas and building of coastal defences and other activities linked to urban expansion are giving rise to alterations of coral reefs, shorelands, beachfronts and the seafloor.

Important habitats are being destroyed. Wetlands are being transformed into agricultural lands and through coastal development. Tourism, unrestricted and uncontrolled aquaculture, clearance of mangroves and destructive fishing practices, such as the use of dynamite and chemicals, are also causing the physical destruction of important habitats. The introduction of alien species can also have serious effects upon marine ecosystem integrity. Spawning grounds, nurseries and feeding grounds of major living marine resources of crucial importance to world food security are being destroyed. This destruction of habitat exacerbates over harvesting of these living marine resources leading to a growing risk that they are being depleted. This is an increasing threat to the food security of coastal populations, in particular in developing countries.

The damming of river systems can result in upstream sedimentation, possible changes in estuarine conditions and interference with fish migration. These adversely affect biological diversity and biological productivity. The practice of saltwinning from saltpan construction in coastal areas can also affect salt concentration levels and biological diversity.

UNEP Global Plan of Action for the Protection of the Marine Environment from Land Based Activities <enter>

GIWA definition

The modification of ecosystems or ecotones is one of the most difficult issues to quantify. This is partly due to spatial and temporal heterogeneity and partly to the insufficiency of knowledge of species composition. The indicators defined provide a basis for determining the severity of the changes in the past 3 decades. They recognise our inability to identify some individuals beyond the family level and emphasise the importance of extinction and introductions as well as changes in individual native species. They also recognise that the loss of a native species from a system with low diversity may be more significant than from a highly diverse one.

Environmental impacts

1. Modification of natural productivity

2. Modification of biodiversity including loss of species and genetic diversity

3. Changes in ecosystem stability

4. Changes in community structure both plant and animal

5. Susceptibility to disease

6. Changes in migratory species populations and migratory patterns

7. Modification in natural storm barriers and reduced protection from erosion

8. Increased vulnerability to opportunistic invaders

GIWA habitat classification scheme

To enter the GIWA water habitat classification scheme index for Issue 13: Modification of ecosystems or ecotones, including community structure and/or species composition, please click here or from the hyperlink at the bottom of this page.

The GIWA habitat classification scheme is divided into 2 categories:

1. Freshwater

2. Marine

GIWA Habitat Classification Scheme Index for Issue 13

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