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Rapid Appraisal of Riparian Habitat Condition across Northern

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					A Rapid Method for Assessing the Condition of Riparian Zones in the Wet/Dry
Tropics of Northern Australia.
Ian H. Dixon1, Michael M. Douglas1, John L. Dowe2, Damien W. Burrows2 and Simon A. Townsend3

1 Tropical Wetland Program, Charles Darwin University, Darwin NT, 0909, ian.dixon@cdu.edu.au, michael.douglas@cdu.edu.au
2 Australian Centre for Tropical Freshwater Research, James Cook University, Townsville, Qld, 4811, john.dowe@jcu.edu.au,
damien.burrows@jcu.edu.au
3 NT Department of Infrastructure, Planning and Environment, PO Box 30, Palmerston NT, 0831, simon.townsend@nt.gov.au



Abstract
The health of riparian habitats across northern Australia is becoming increasingly important to its diverse
land management community. Assessing, protecting and improving the condition of riparian habitats has
been and will continue to be a major activity focus of regional planing in northern Australia. However, a
lack of information on assessing the health of savanna riparian zones has resulted in little evaluation of the
effectiveness of existing programs or the prioritisation of works for future programs. Many methods already
exist to assess riparian health, but their application is often limited to specific areas or projects and purposes.
Consideration of the vast river lengths present in northern Australia, often in remote areas, led us to develop
a rapid appraisal method suitable for trained non-specialists to assess savanna riparian health. The method is
being applied across northern Queensland and the Northern Territory and is comprised of attributes of
vegetation cover, woody debris, weediness, native plant regeneration and evidence of disturbance. It is
based on methods developed by Werren and Arthington (2002) and Jansen et al. (2004) and has been
modified for the different conditions of northern Australia. It provides a consistent approach across large
geographic areas and should help to assess and improve management of savanna riparian zones in pastoral,
mixed use and conservation managed lands across northern Australia.


Keywords
Rapid appraisal, riparian habitat, vegetation condition, savannas.


Introduction
Riparian zones are vital elements of the landscape in the savannas of northern Australia. Their contribution
to biodiversity, cultural values and the economy is disproportionately large considering the small area that
they occupy (Finlayson 2001, MacLeod 2001). Savanna riparian zones are vulnerable to disturbances such
as weed invasion, feral animals, fire, overgrazing and erosion (Burrows 2001, Choquenot et al. 2001,
Douglas and Pouliot 1997, Grice 2001). Maintaining and improving the condition of riparian zones is likely
to be identified as a high priority in most of the natural resource management plans that cover Australia’s
tropical savannas. From many points of view, it is desirable and widely recognised that a method for rapidly
assessing the health of numerous riparian locations across large geographic areas is required for a wide
variety of management goals, including the need to demonstrate the positive effects of natural resource
management activities undertaken through Landcare, Natural Heritage Trust (NHT II) and related programs.

Savanna riparian zones are spread out across a vast area (approximately 25% Australia), much of which is
remote from major population centres and is characterised by a low population density. A rapid appraisal
approach to assessing riparian condition may be best, as too few technical experts are likely to be available to
cover such a large area. Rapid appraisal methods can be undertaken by trained non-specialists to assess and
monitor environmental conditions and they can be completed relatively quickly, simply, and inexpensively
(Ward et al. 2003). A rapid appraisal typically requires the operator to score simple indicators of health
using visual estimates to derive an index of condition (Innis 2000, Werren and Arthington 2002). When used
by a trained operator, results obtained from a rapid appraisal are easily interpreted and highlight areas of
ecological concern, and when repeated over time they can be used to monitor changes in condition. They
may also be used to prioritise areas that require more detailed investigations.

Many such methods already exist (eg, Table 1), with most only being used for specific studies in limited
locations. There is currently no rapid appraisal method which has been developed and tested for use across
northern Australia. The need for a standardised approach to assess riparian health that would be adopted
across a broad range of user groups, from scientists to on-ground land managers, was recognised and a
program set out to achieve this goal. The Tropical Savannas Cooperative Research Centre (Charles Darwin
University, Australian Centre for Tropical Freshwater Research, NT and Qld Governments and CSIRO) and
Land & Water Australia are currently developing the Tropical Rapid Appraisal of Riparian Condition
(TRARC) which is being tested and applied in Queensland and the Northern Territory. This paper outlines
the process used to develop the method and the choice of indicators.

Developing the TRARC
The program began with a review of existing riparian assessment methods (Table 1). Most of these methods
use a similar set of attributes to assess riparian vegetation condition. Several include riparian vegetation as a
sub-index of a broader assessment of stream condition (eg, Bjorkland et al. 2001, Chessman 2002, Ladson et
al. 1999), although with varying degrees of consideration given to vegetation indicators.

Table 1. Examples of Australian and north American methods of riparian vegetation assessment
considered for testing in tropical savannas.

 Method                                                     Region        Source
                                                                          (Jansen et al. 2004, Werren and
 Multi-metric rapid assessment of riparian habitat          Qld, NSW
                                                                          Arthington 2002)
 Multi-metric bioassessment of streams with 4-7             NSW, Vic,     (Chessman 2002, DEWA 2003,
 components—including riparian zone                         WA            Ladson et al. 1999)
 Detailed survey of stream bed, banks, aquatic and                        (Anderson 1993, Faulks 1998,
                                                            Qld, NT
 riparian habitats                                                        Faulks 2001)
 Bioassessment and predictive modelling of streams
                                                            Australia     (Lloyd and Cook 2002)
 with 6 components—including riparian zone
 Multi-metric rapid assessments of streams with 9-15                      (Barbour et al. 1999, Bjorkland et
                                                            USA
 components—including riparian vegetation                                 al. 2001, Ward et al. 2003)

The two methods considered most suitable (Jansen et al. 2004, Werren and Arthington 2002) were both
developed specifically as rapid appraisals and have a strong focus on riparian vegetation condition. The
method of Werren and Arthington (2002) was designed for the wet tropical coasts of NE Queensland
whereas the method of Jansen et al. (2004), the Rapid Appraisal of Riparian Condition or RARC, has been
used extensively in SE Australia (eg, Jansen and Robertson 2001). Both methods were tested in pilot trials
in the Darwin region and in Kakadu National Park, Northern Territory, where researchers and land managers
considered whether the methods would be: (1) user-friendly to the diverse land management community of
northern Australia; (2) robust in a distinctly wet/dry seasonal environment; and (3) responsive to significant
land development issues across the savannas. Following the trials, it was felt that these methods needed
some modification to ensure that they would be reliable given the following features of the region:
pronounced effects of seasonality on the vegetation; frequent fire events; regular, recurrent wet season flood
events; lower diversity in land use patterns (generally dominated by cattle grazing); and, lower occurrence of
exogenous impacts.

A workshop was held at James Cook University, Townsville, in October 2003 where riparian ecologists
agreed on a framework for developing the Tropical Rapid Appraisal of Riparian Condition (TRARC). The
workshop participants determined which habitat indicators would be important to measure in savanna
riparian zones and how best to measure them. Methods were formulated to provide a balance of accuracy,
time, cost and ease-of-use (Dixon et al. 2004). Despite these alterations, the approach developed in this
workshop is very similar to the RARC method of Jansen et al. (2004), thus giving it considerable
comparability to the methods currently being developed for south-eastern Australia. The TRARC method
developed from that workshop was trialled in the Northern Territory and Queensland—Darwin Region
(Dixon and Douglas 2004), Douglas-Daly Region, Kakadu National Park, Victoria River District and the
Burdekin River catchment (Dowe et al. 2004). These tests identified the need to make further refinements to
improve accuracy and ease-of-use, and to cater for seasonal variation of vegetation growth.
The program to develop the TRARC is currently in its second of three years. Once the developmental phase
is completed, application of the methods across northern Australia will commence as phase two. The
following section outlines our current progress.


The TRARC framework to date
The TRARC is a tool which gauges how well the riparian zone performs specific functions. It requires the
operator to visually assess 21 indicators of riparian condition (Table 2) which were chosen to reflect the
various functions of a riparian zone, such as those described by (Naiman and Decamps 1997):

•   Wood and leaves falling into the stream from riparian plants slows the stream down while the roots of
    riparian plants bind the soil. This helps to stabilise the stream banks.
•   Leaves, fruit, flowers, and seeds that fall into streams provide food for aquatic animals.
•   Wood, leaves, fruit, flowers, and seeds from riparian plants provide important habitats for aquatic plants
    and animals.
•   Shade provided by riparian plants regulates the temperature and the amount of light reaching the stream
    water. This can affect the stream’s productivity, the growth of aquatic plants, and the animal species that
    survive.
•   The riparian zone helps to maintain good stream water quality. Water from the catchment passes
    through the riparian zone before reaching the stream. The riparian vegetation slows its passage, allowing
    sediments, nutrients and pollutants to be trapped and filtered.

Indicators are grouped into five sub-indices: cover, debris, natives, regeneration and disturbance. Each
indicator is given a score, from 0-4, based on pre-defined condition categories (Table 2). Condition
categories are based on the percentage cover, abundance or extent of the indicator. Scores for each sub-
index are converted to a relative score out of 100, where higher scores indicate better riparian habitat
condition. A summary of overall riparian condition is derived by summing all indicator scores, with a
maximum score of 100. A detailed procedure for data analysis is under development and will be finalised in
a future workshop.

Table 2. An abbreviated framework of the TRARC. Twenty one indicators are grouped into five sub-
indices. Each indicator is given a score between 0-4. Indicators marked with (*) have their score
doubled. Final summary score is the sum of all indicators (maximum score = 100).

                                                               SCORE
             * scores double weighted     0           1           2                       3              4
                                     COVER (maximum score = 28)
•   Riparian width (amount cleared)*    major     major/mod mod/minor                   minor       uncleared
•   Canopy continuity                   <30%       30-55%      55-75%                  75-90%       90-100%
•   Overstorey cover                    absent      1-30%      30-60%                  60-85%       85-100%
•   Ground cover                        absent      1-30%      30-60%                  60-85%       85-100%
•   Grass cover                         absent      1-30%      30-60%                  60-85%       85-100%
•   Bare ground                        100-75%     75-50%      50-25%                  25-5%          <5%
                                     DEBRIS (maximum score = 16)
•   Fine woody                          absent      1-30%      30-60%                  60-85%        85-100%
                                                                                      1 tree OR      1 tree &
• Coarse woody *                            absent       1-2 logs       3-5 logs
                                                                                       >5 logs        >5 logs
• Standing dead                        >25%          x        25-5%                        x           <5%
                                   NATIVES (maximum score = 16)
•   Overstorey                         absent     1-30%       30-60%                  60-85%         85-100%
•   Ground cover                       absent     1-30%       30-60%                  60-85%         85-100%
•   Grass                              absent     1-30%       30-60%                  60-85%         85-100%
•   Deleterious weeds (from list)     4 species  3 species   2 species                1 species      0 species
                                REGENERATION (maximum score = 20)
•   Dominant canopy juveniles *        absent        1          2-5                     6-20           >20
• Sub-dominant juveniles *                  absent      1         2-5                    6-20            >20
                                                       no        little                  some           large
• Community structure                  trees absent
                                                    variation  variation               variation      variation
                                  DISTURBANCE (maximum score = 20)
•   Slumping erosion                     100-50%    50-25%      25-5%                    5-1%          absent
•   Gully erosion                        100-50%    50-25%      25-5%                    5-1%          absent
•   Fire impact                          abundant   frequent  occasional                  rare         absent
•   Animal impact                        abundant   frequent  occasional                  rare         absent
•   Other impact                         abundant   frequent  occasional                  rare         absent


Future development of the TRARC
Development of the TRARC will continue over the next two years to ensure the methodology is accurate,
repeatable and user-friendly, and that the data analysis produces final scores that are truly representative of
the riparian condition. Further trials will be undertaken to specifically address the following questions: (1)
how many sites are needed to give a fair representation of a particular reach?; (2) how sensitive is the method
to inter-operator variability?; (3) how do potential end users respond to applying the method?; and (4) do
results from the TRARC reflect those derived from other indicators of riparian and stream condition?

The collaborative development of this method by a range of savanna researchers and stakeholders across
northern Australia will ensure that a unified approach is taken to evaluate riparian condition. However, we
recognise that the method may well need to be modified for use in different bioregions or for specific
projects. The TRARC is likely to be adopted by a diverse range of users including government agencies,
park rangers, indigenous land managers, pastoral land managers, private consultancies and Landcare groups.
Each of these groups may have different reasons for assessing their riparian condition and different values of
riparian health. Therefore, the initial outcome of the project will be to develop a standard ‘template’ that can
be modified and calibrated for different purposes.

This ‘template’ is currently being used by two research/monitoring groups in markedly different
biogeographical regions in northern Australia: the Australian Centre for Tropical Freshwater Research in a
catchment-wide assessment of the Burdekin catchment, Qld; and, the NT Department of Infrastructure,
Planning and Environment – Water Monitoring Branch in their monitoring of streams flowing into Darwin
Harbour and in the Douglas-Daly catchment, NT. Results from these programs have supported the
envisaged need for regional calibration of the TRARC if it is to be comparable across northern Australia.
Future workshops will address this need.


Conclusion
The TRARC provides a simple tool for obtaining an assessment of riparian condition. This will help those
involved with land management to document improvements in riparian condition due to conservation and
restoration programs and highlight areas of ecological concern that need priority for future programs. The
use of rapid appraisal methods hold several benefits for riparian management. Developing a method that
non-specialists can use that provides easily interpretable results will act as an educational tool, thus
increasing understanding of ecological interactions in riparian zones. Land managers who gain knowledge
of the riparian zone and actively participate in its assessment, maintenance and monitoring may be more
likely to encourage others to do so. The greater the network of land managers who adopt the methods, the
greater the potential for sustainable land use across the savannas. The comparability between this method
and that developed and implemented in several large areas of SE Australia (i.e. Jansen et al. 2004) will also
enable comparability across these areas and the potential to develop into a national approach.

Acknowledgements
We thank the Tropical Savannas Cooperative Research Centre and Land and Water Australia for financial
support. Staff at NT Department of Infrastructure, Planning and Environment and Kakadu National Park
provided valuable assistance and feedback on preliminary trials. Garry Werren, Tony Grice, John Ludwig,
Samantha Setterfield, Sally Mitchell and Amy Jansen provided valuable contributions to the development of
this approach. Thank you to Rod Knight and an anonymous reviewer for making valuable comments on a
draft of this paper.


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