WETLAND REHABILITATION: SUCCESS OR FAILURE

Posted on 18 Mar 2022

Wetlands are known to provide several Ecosystem Services (ESS) to the direct natural environment and surrounding human communities. In South Africa, wetlands around the country have been degraded by human induced activities such as agriculture and residential development. Recent figures provided by Working for Wetlands indicate that South Africa has lost approximately 50 % of the original wetland habitat area within the Republic. Of the remaining wetland ecosystems, approximately 48 % are Critically Endangered, 12 % are Endangered, 5 % are Vulnerable and 35 % are Least Threatened (Working for Wetlands, 2021). In a country that is freshwater stressed the continued degradation of wetlands will result in a lower yield of agricultural productivity, reduction in clean water, higher potential for flooding of properties, and reduce the opportunity for endangered flora and fauna to thrive within the unique wetland habitats.

 

An important mechanism used to manage the current integrity and functionality of wetlands within South Africa is the rehabilitation of degraded systems. Department of Water Affairs (DWAF) (2009) defines rehabilitation as “the process of reinstating natural ecological driving forces within part of the whole”.  By rehabilitating a wetland its overall functionality and integrity can be improved, and resultantly the ESS provision of the system. However, wetland rehabilitation can be a success or failure dependent on the strategy, interventions and monitoring that is conducted. It must be noted that rehabilitation is not a static end-point of a recipe-type process (Kusler & Kentula, 1990), but rather a process on its own where an opportunity is provided to the wetland for a new beginning (Grenfell et al., 2007).

 

In order for wetland rehabilitation to be successful the following aspects must be followed as a guide:

 

  • A suitably qualified wetland ecology must conduct a detailed field survey of the proposed rehabilitation site to determine the current extent, Present Ecological State (PES) and ESS delivery potential.
  • Formulate a rehabilitation strategy. Within this strategy the following items must be taken into consideration:
    • The current observed impacts on the wetland,
    • Outline clear aims and objectives for the wetland rehabilitation.
    • Identify interventions (soft and/or hard) that need to be instated to reinstate the wetland to its envisioned post-rehabilitation state. The interventions will be conducted in a specific order for the envisioned post-rehabilitation state to be successful (e.g., if erosion exist within a wetland, backfilling with wetland sediment must be conducted before any revegetation).
  • Lastly, determine the level of monitoring that will need to be conducted on the wetland to ensure that the objectives and goals are achieved. The three (3) different levels of monitoring prescribed by Cowden and Kotze (2009) include:
    • Level 1 – the outputs and basic outcomes of the wetland rehabilitation in terms of physical interventions;
    • Level 2 – the rapid assessments of the rehabilitation outcomes using appropriate assessment tools; and
    • Level 3 – the comprehensive assessment of the wetland rehabilitation outcomes determined by the rehabilitation objectives.

The levels of monitoring are elaborated below.

 

Level 1 Monitoring:

 

Level 1 monitoring generally focuses on the outputs and basic outcomes of wetland rehabilitation, which are generally limited to the implementation phase. The long-term monitoring of the wetland rehabilitation outputs is therefore focused on the assessment of the structural integrity of the interventions, with emphasis on identifying structural vulnerability. The monitoring of the intervention’s integrity and/or vulnerability needs to be undertaken by a SACNASP registered wetland specialist with experience in wetland rehabilitation interventions. Additional requirements of the Level 1 monitoring process include monitoring visual changes of the rehabilitated wetlands.

 

Structural interventions

The assessment of the structural integrity would be undertaken based on the specific criteria outlined and focus on the long-term stability of the interventions and the likelihood of achieving the stated objectives. This assessment would serve to identify weaknesses or strengths of the selected interventions within the wetland habitat. The monitoring intervals for the interventions should coincide with the type of intervention provided by the wetland specialist, and furthermore include event-based monitoring. Event-based monitoring is determined by the design level of the structures. The maintenance of the structures is essential in ensuring the benefits supplied by the wetland are not compromised.

 

Visual assessment

Changes in the visual appearance of the ecosystems can be used to show changes in the systems’ characteristics. A photographic record, utilising a series of photographs, would enable interested parties to track broad-scale vegetation changes (Cowden and Kotze, 2009). In this instance, with the clearing AIPs and the promotion of wetland habitat, the use of a photographic record is considered to be a useful monitoring tool. It is recommended that the photographic record be derived from both:

  • Aerial photographs; and
  • Panoramic and/or site photographs (fixed point photography).

 

Aerial Photographs

Google Earth regularly update their imagery, and this imagery should be used to illustrate the large-scale changes in the watercourses following the implementation of the rehabilitation and on-going management. In this instance, aerial imagery is likely to illustrate the changes linked to the rehabilitation, for example: plugging of artificial drains, clearing of AIPs and the promotion of wetland habitat.

 

Fixed Point Photography/Site Photographs

Panoramic photographs from an overview point in combination with Fixed Point Photography (FPP) would provide useful indications of the changes at both a landscape and within-system level. These photographs would be taken pre- and post-implementation and should be collected in accordance with the guidelines outlined in WET-Rehab Evaluate (Cowden and Kotze, 2009). Photographs should be taken up and downstream of each proposed intervention, both pre- and post-implementation.

 

Level 2 monitoring

 

The rapid assessment of the wetlands functionality and integrity would assist in illustrating any benefits/deficits associated with the rehabilitation activities. This would be undertaken for the current and post-rehabilitation scenarios, utilising the WET-EcoServices (Kotze et al. 2009) and WET-Health (Macfarlane et al. 2008) assessments techniques. A Wetland Delineation and Functional Assessment (WDFA) must be compiled in order to determine the current conditions which would serve as the baseline data to which post-rehabilitation assessments will be compared. To ensure accuracy of the assessments undertaken, the practitioner should have an understanding of general wetland functioning and the conditions specific to the site itself, such as the origin of the wetland, how it would function in its natural state, and what factors are affecting its functioning and integrity.

 

Assessment of ecosystem services

WET-EcoServices is used to assess the goods and services that individual wetlands provide, thereby aiding informed planning and decision-making (Kotze, et. al., 2009). The tool provides guidelines for scoring the importance of a wetland in delivering each of 15 different ecosystem services (including flood attenuation, sediment trapping and provision of cultural services). Ecosystem service delivery must be assessed at Level 2, based on a field assessment of key descriptors (e.g. flow pattern through the wetland). The ecosystem services, which include the direct and indirect benefits supplied by the wetland to the surrounding environment and communities, are assessed by scoring various characteristics of the wetland and the surrounding catchment according to the following scale:

  • Low (0);
  • Moderately low (1);
  • Intermediate (2);
  • Moderately high (3); and
  • High (4).

 

The overall goal of assessing the post-rehabilitation state of the wetlands with the use of WET-EcoServices is to reveal the improvement or deterioration of the wetland at supplying ecosystem services. This will be determined by comparing the post-rehabilitation scores to the baseline assessment scores. This allows for more informed planning and decision making.

 

Assessment of ecosystem integrity

The assessment of ecosystem integrity must be undertaken using the WET-Health assessment technique, which was developed for southern African wetlands (Macfarlane et al., 2008). WET-Health is a tool designed to assess the health or integrity of a wetland. Wetland health is defined as a measure of the deviation of wetland structure and function from the wetland’s natural reference condition. In the case of the proposed rehabilitation plan, it will be used to compare the integrity of the wetland systems before and after rehabilitation (post-construction). This technique attempts to assess hydrological, geomorphological and vegetation health in three separate modules.

 

Level 3 monitoring

 

Level 3 monitoring involves an in-depth, comprehensive assessment of the wetland rehabilitation outcomes by measuring certain indicators at a finer resolution, greater frequency and over a longer period of time. Since this level of monitoring is more intense and specific to various aspects of a system, such as vegetation identification, it would typically require specialist input. According to WET-Rehab Evaluate (Cowden and Kotze, 2009), this level of monitoring may be required where:

  • The wetland rehabilitation objectives require a finer level of monitoring;
  • The wetland has been prioritised to be of importance;
  • The potential benefits of a finer scale investigation are great; and
  • The wetland is of high importance.

 

Level 3 monitoring assesses at a finer and more intensive level, the project’s attainment of the outcomes of the wetland rehabilitation activities. This level of monitoring may be selected for projects where:

  • The wetland rehabilitation objectives for the project call for a fine level of monitoring (e.g. increased population of a certain fish species);
  • Uncertainty exists in terms of achieving the objectives, and opportunities for gaining new insights are potentially great;
  • The project has relevance to key research questions, as well as being accessible to research bodies and personnel;
  • The prioritisation outlined in the rehabilitation process; and
  • The wetland to be particularly important, or the wetland is found to be functionally important.

 

The correct and continuous monitoring of any rehabilitation intervention must be conducted in order for corrective actions to be implemented that will alter the rehabilitation trajectory towards the planned end-goal/condition. Typically, if the rehabilitation strategy, interventions, and monitoring are conducted as per the Wetland Rehabilitation Plan, which must be conducted by an qualified Wetland Specialist with several years of experience, rehabilitation of the wetland can be a success.

 

There are key principles for successful wetland rehabilitation which are:

  • Removal of the cause of damage and management of the resource correctly.
  • Where water flow patterns have been disturbed, these should be reinstated to natural or near natural condition.
  • Concentration flows should not be conducted as far as possible.
  • Soil erodibility potential should be determined when constructing structures through wetlands (e.g: roads and dams).

 

The main reasons that rehabilitation is not successful in wetlands are:

  • The Wetland Rehabilitation Plan was not conducted by an accredited Wetland Specialist with several years of experience.
  • The strategy, intervention and monitoring outcomes outlined in the Wetland Rehabilitation Plan are not understood by the contractors and land surveyors.
  • There is not enough budget to conduct the relevant rehabilitation interventions.

 

In conclusion, the successful rehabilitation of a degraded wetland ecosystem is possible if the rehabilitation plan is developed by a suitably qualified professional who has cognisance of the current and future functionality and integrity goals of rehabilitation. It is imperative that an adaptive management strategy be implemented throughout, as biophysical characteristics and influence from external stakeholders will need to be continually managed to ensure the end-goal is achieved.

 

Reference

COWDEN, C. AND KOTZE, D. C. 2009. WET-RehabEvaluate: Guidelines for the monitoring and evaluation of wetland rehabilitation projects. WRC Report no. TT 342/88, Water Research Commission. Pretoria, South Africa.

 

DEPARTMENT OF WATER AFFAIRS (DWAF). 2009. General authorisation in terms of Section 39 of the National Water Act, 1998 (Act no 36 of 1998) in terms of Section 21(c) and (i) for the purpose of rehabilitating a wetland for conservation purposes.

 

GRENFELL, M.C., ELLERY, W.N., GARDEN, S.E., DINI, J. AND VAN DER VALK, A.G. 2007. The language of interventions: A review of concepts and terminology in wetland ecosystem repair. Water SA, 33: 43-50.

 

KOTZE, D.C., MARNEWECK, G.C., BATCHELOR, A.L., LINDLEY, D.S. and COLLINS, N.B. 2008.  WET-Ecoservices: A technique for rapidly assessing ecosystem services supplied by wetlands. WRC Report No TT 339/09, Water Research Commission, Pretoria

 

KUSLER, J.A. AND KENTULA, M.E. 1990. Wetland creation and restoration: The status of the science. Island Press, Washington, DC. 594pp.

 

MACFARLANE, D.M., KOTZE, D.C., ELLERY, W.N., WALTERS, D., KOOPMAN, V., GOODMAN, P. & GOGE, C.  2009. WET-Health: A technique for rapidly assessing wetland health, Version 2. WRC Report No TT 340/09, Water Research Commission, Pretoria.

 

WORKING FOR WETLANDS. 2021. Working for Wetlands: 20 years of wetland restoration in South Africa.

 

Appendix A: Example of successful rehabilitation

 

Figure 1: An example of the use of aerial photography to monitor the condition of the rehabilitated wetland habitats subsequent to the implementation of the proposed rehabilitation activities. A- Lack of wetland vegetation and surface roughness (indicated by red arrow) and B- Revegetation with hydric indigenous vegetation in the same area (indicated by red arrow).

 

Appendix B: Example of failed rehabilitation

 

Figure 2: An example of the use of aerial photography to monitor the condition of the rehabilitated wetland habitats. A- Wetland area that’s within sugarcane plantation that requires rehabilitation and B- Complete removal of vegetation within wetland and minor catchment, further channelization of wetland for development purposes.