Stressor model overview

How do we monitor pressure and condition?

The wetlands assessment framework developed as part of the Queensland Wetlands Program provides a structure to monitor the pressure on, and condition of, wetlands through a stressor based framework.

What are stressors?

Stressors are defined as components of the environment that when changed can affect the condition of the ecosystem. These can be natural components such as nutrients or entirely anthropogenic components such as litter (rubbish) or biota removal/disturbance. Some stressors, such as toxicants, may have natural (e.g. particular metals) and anthropogenic (e.g. pesticides) aspects.

Why use a Stressor-based wetland assessment framework?

The design of an assessment framework is largely dependent on its objectives. The objective of this lacustrine and palustrine assessment framework is to develop a statewide process that can assist in their management by:

1. Reporting on the overall condition of, and pressure on, Queensland’s wetlands based on a pressure-impact assessment framework
2. Reporting on change in these conditions and pressures over time
3. Improving current understanding of processes and components of the wetland ecosystem that relate to condition
4. Guiding natural resource management decision-making processes by identifying the likely causes of any observed impact on wetland condition.

For each stressor, the following linked elements are identified:

1. Human activities that result in a change to the stressor
2. The actual factor directly related to the stressor that is changing. For example, the actual nutrient load entering the wetland
3. The change in physical-chemical state observed in response to a stressor
4. The biological impact observed as a response to the change in physical-chemical state.

These elements provide a logical framework for the selection of indicators. For each stressor, one or more indicators of each element can be identified.

The employment of this framework is dependent on a good conceptual understanding of the processes occurring in catchments and wetlands.  The framework directly links the pressures on the environment (as a result of human activities), to biological impacts and changes in the physical-chemical state of the environment.

Stressor Models

Stressor models are used to show how human activities interact with the natural processes occurring in a wetland (i.e. process models) and impact the ecosystem. This allows pressure and condition indicators to be determined that are specific to a particular stressor and wetland type.

In Queensland, the following key components have been identified as major stressors, important in lacustrine and palustrine ecosystems:

• Aquatic sediments
• Bacteria/pathogens
• Biota removal/disturbance
• Conductivity
• Connectivity
• Habitat removal
• Hydrology
• Litter (rubbish)
• Nutrients
• Organic matter
• Pest (animal, plant) species
• pH
• Toxicants

A 14th stressor has been identified, and models constructed, but is currently thought to be of little importance in Queensland’s wetlands:

• Water temperature

Bibiolography and Further reading

The Conservation Measures Partnership (CMP) is a partnership of conservation organizations that seek better ways to design, manage, and measure the impacts of their conservation actions.