All roads lead to WSUD: exploring the biodiversity ...

All roads lead to WSUD: exploring the biodiversity, human health and social benefits of WSUD John Dahlenburg* and Phillip Birtles* *Sydney Metropolitan Catchment Management Authority, P O Box 3720, Parramatta, NSW 2124 Australia (Email: [email protected], [email protected] )

ABSTRACT A great deal of research has been, and is still being, undertaken to justify the implementation of Water Sensitive Urban Design (WSUD) for water quality and flow benefits. More recently, the benefits for undertaking WSUD to help counter the urban heat island effect has also been investigated. These three issues are often used as “promoters” or benefits to justify WSUD, sometimes with mixed success. It appears that sometimes this may be because decision makers either don’t have an affinity with, interest in or understanding of the WSUD “promoters” currently being used. When trying to “sell” WSUD to key decision makers it would appear better to have as wider range of benefits or “promoters” as possible to improve the chances of one or more of these resonating with the decision makers. To help expand this repertoire of benefits for implementing WSUD this paper will draw on other research being undertaken, often in unrelated areas that could help add additional “promoters” or reasons/benefits for implementing WSUD. The biodiversity benefits of plant selection in WSUD devices will be explored through a case study being undertaken in the Cooks River Catchment in Sydney. This paper will also review research on the importance of “green spaces” in urban environments to human health and social capital/interaction.

KEYWORDS WSUD, urban biodiversity, human health, green space, social interaction, Sydney.

INTRODUCTION It is highly likely that urban green spaces (even small retrofitted WSUD devices) will become more important to our cities in the future. The urbanisation of populations world-wide is increasing rapidly and a further 2.9 billion people are expected to be urban dwellers by 2050 (UN, 2009). This means that the urban areas of the world are expected to absorb all the population growth over the next forty years as well as attracting people from rural areas (UN, 2009). In Australia, already one of the most urbanised countries in the world, urban density is continuing to increase in our major capital cities. In Sydney for example, the recent and expected medium-term urban development growth to 2031 will continue to be split roughly 70% in existing urban areas and 30% in new greenfield release areas (NSW Planning, 2010). This urban consolidation along with changing social interaction and travel patterns such as more virtual interactions/socialisation and more flexible work arrangements that don’t require employees to commute to a central location daily is likely to change people’s expectations of urban spaces. Recent studies have shown that “total passenger kilometres in motorized modes, has slowed its growth relative to GDP and even declined in per capita terms in some countries” (Millard-Ball and Schipper 2010 p. 371) and people are postualing that we, in the developed world, may have reached “peak travel”. These trends are likely to mean that

7th International Conference on Water Sensitive Urban Design, February 2012 Melbourne, Australia ___________________________________________________________________________________________

localised environments will become more important and valued parts of the urban fabric as people increase their time spent locally. Research undertaken to validate, justify and promote Water Sensitive Urban Design (WSUD) has understandably been focused around the area first associated with its genesis, namely water quality improvement (WSUD Research Group 1990; Newman 1994; Mouritz 1996; Evangelisti 1996). This was followed by research into the ecological and physical impacts of stormwater on urban streams (Walsh, Roy et al. 2005). More recently research has been undertaken to examine the influence WSUD might have on micro-climate and also reducing the urban heat island effect in cities. This significant body of research has become the foundation for much of the promotion, justification and “selling” of WSUD to professionals, decision makers and the community. This has meant WSUD has primarily been promoted or justified from a techno-scientific perspective. A great deal of research has also been conducted in the area of capacity building and institutional governance to support WSUD implementation (Brown, Mouritz &Taylor 2006; Dahlenburg & Lees 2004, Dahlenburg 2006; Keith & White 2006). It could be argued that this method of justification has been successful at enabling progressive public and private organisations with an appetite for risk to pilot WSUD in many major urban centres in Australia. In most cases it seems that to achieve this, a top down approach has been taken with little genuine engagement with local communities, policy makers or political representatives (Dahlenburg & Morison, 2009). If we are to progress towards the goal of achieving truly water sensitive cities (Brown, Keith & Wong 2009) then it seems a greater emphasis on genuine engagement with our communities, policy makers and politicians will be vital. To realise this, a greater swag of less techno-scientific “promoters”, justifiers and benefits will need to be developed/researched that resonate with, or are more socially attuned to the interests of a more diverse range of people. To help expand this repertoire of benefits for implementing WSUD this paper will draw on other research being undertaken, often in unrelated areas that could help add additional “promoters” or reasons/benefits for implementing WSUD. It will explore the biodiversity benefits of plant selection in WSUD devices through a case study being undertaken in the Cooks River Catchment in Sydney. It will also review research on the importance of “green spaces” in urban environments to human health and social capital/interaction.

RESULTS AND DISCUSSION Could inclusion of WSUD help improve human health? A number of studies have been undertaken in several countries that show a link between green space in urban environments and impacts on human health (Maas et al. 2009; Fan, et al 2011; Cooper, Boyko & Cooper, 2011; Bell et al 2008), (Mitchell, Astell-Burt et al. 2011). Also two recent studies (Bowler, Buyung-Ali et al. 2010), (Lee & Maheswaran 2011) that reviewed the evidence of a number of studies looking at relationships between green space in urban areas and mortality had findings that generally supported a beneficial health effect. The greatest benefits shown are for anxiety, attention, sadness/depression, anger and fatigue/energy (Bowler, Buyung-Ali et al. 2010). The study by Maas et al. 2009 that included data for a population of around 350,000 people in Holland found that non-communicable disease clusters were lower in areas with more green space located within a 1 km radius of living environments. A graphical representation of the results of this study can be found in

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Figure 1 below. These effects were strongest for children and people living in lower socioeconomic conditions. They also found a strong relationship between anxiety disorder and depression and the amount of local green space, which suggests mental health is particularly likely to be affected by the amount of accessible green space. In addition, they postulated that “an increase of 1 percentage point of green space on physician-assessed morbidity equals the effect of 1-year lower age”. (Maas et al. 2009 p.970). It has also been found that views onto a natural environment from hospital rooms can aid patients in their recovery (Ulrich, 1984) Recorded disease prevalence per 1000 people in environments with differing amounts of green space

**MUPS Acute urinary tract infection Migraine/severe headache Asthma, *COPD

90% Green Space

Diseases

Upper respiratory tract infection

10% Green Space

Anxiety disorder Depression Severe neck & shoulder complaints Severe back complaints Neck & back complaints High blood pressure Cardiac disease 0

50

*COPD – chronic obstructive pulmonary disease **MUPS – medically unexplained physical symptoms

100

150

200

250

Disease rates per 1000 people

Figure 1 Disease prevalence and amount of green space (created from Maas et al. 2009) The findings of the research discussed provide an additional justification for implementing WSUD, particularly retrofitting it into dense urban environments and should be used as an additional benefit or “promoter”. Human health is a topic that tends to resonate with a wide range of people and decision makers in particular. Also given the economic and social benefits that will accrue to society via improvements in human health (mental and physical) it should be included in the justification or cost-benefit analyses of WSUD projects. Could WSUD help improve urban biodiversity? Our urban waterways are important biodiversity corridors that often pass through the heart of our urban centres, connecting coastal waters and estuaries to freshwater streams and sometimes distant undisturbed catchments. In Sydney, the small creeks and adjacent riparian lands are often the only remaining examples of pre-european vegetation communities. Historically, they were maligned by urban developers due to steep terrain or flooding characteristics (Bourne 2001). WSUD offers an opportunity to link and remediate these

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vegetation corridors and capitalise on the high non-use value that urban residents already place on these “refuges” of biodiversity. When a management plan was developed by local government for Wolli Creek in the densely urbanised Inner South of Sydney, the receiving environment of local stormwater infrastructure was specifically defined as the riparian vegetation communities themselves rather than the creek1. Elevated nutrients levels in bushland soils are strongly associated with exotic weed infestation and meisc shifts in native vegetation communities (Leishman et al 2004). Stormwater interventions recommended in the plan were prioritised by two key factors (SMCMA 2011): • modelled annual loads of Phosphorus being delivered to riparian soils from stormwater and sewer overflows (see figure 2); and • the condition and status of the existing vegetation at the outlet point. This departure from waterway water quality parameters is one example of how WSUD can be re-focused to improved terrestrial biodiversity outcomes.

Figure 2 Assessment of Phosphorus loads entering the riparian area of lower Wolli Creek from local subcatchments. This data was used to prioritise WSUD stormwater interventions with a goal of improving native vegetation communities (SMCMA 2011) The Sydney Metropolitan Catchment Management Authority (SMCMA) has also recently begun requiring local provenance plants and extensive species lists to be used in all retrofitted WSUD devices it has co-funded in the Cooks River Catchment. This was informed by historical vegetation mapping by Benson et al. (1999) from the Royal Botanical Gardens Sydney and dedicated local nursery professionals who grew the native stock. Typical plantings for a bioretention system include a mix of 10-20 species all collected from within the catchment (100km2). The benefits to the SMCMA and councils of using local provenance plants, has been the higher plant survival and higher growth rates observed in the WSUD systems. This specification is also likely to make these systems more resilient to climate variation, will further contribute to carbon management measures by capturing carbon in the 1

this approach was suggested in Walsh et al (2007)

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soils and plant material and directly increases habitat biodiversity values with in the structure itself. Importantly, local provenance stock ensures the genetic integrity of any native seed or plant material that flows from the systems in overflow events. Stormwater WSUD systems often sit at the “headwaters” of the catchment and planting specifications have the potential to hamper or bolster the efforts of government and community working to restore vegetation communities in downstream riparian lands. Native plants from more ambiguous seed sources establishing downstream could create a complex identification task for bushland professionals and dedicated volunteers in their future restoration efforts. Studies done on biodiversity changes associated with street scale bioretention systems in Melbourne (Kazemi, et al. 2009) show that inclusion of these WSUD devices in urban areas results in increased biodiversity when compared to grassed or garden bed areas. It is worth noting that bushcare in Sydney is a significant social expression of the urban community’s desire to interact with their local landscape (see following). However, the connection between good stormwater (and waste water) management through WSUD and the biodiversity outcomes desired by these volunteer groups is generally not capitalised on by bushland managers nor engineers/stormwater managers. Could WSUD lead to increases in social capital and interaction? A recent study by Lundy & Wade (2011) investigated the urban ecosystem services provided by urban waterways and found that urban waterways contribute to the delivery of a number of supporting, provisioning, regulating and cultural ecosystem services in urban areas. They have used an ecosystem services assessment framework (Millennium Ecosystems Assessment, 2005) to assess the multiple benefits (social and ecological) that could be achieved from urban WSUD projects. This research offers a useful assessment framework that can be used to investigate and promote our urban WSUD projects as multi-functional components of the urban fabric of our cities. It also offers an opportunity to show the linkages and interdependencies that exist between our social and ecological systems. In addition, it allows for the community to see that the environment is not something that exists outside the boundaries of our cities, but is an integral part of its fabric. This “reconnection” to natural systems in urban environments is one of the added benefits WSUD implementation can bring to the community. The need to reconnect to nature in our cities is apparent when you look at the number and variety of individuals and groups that are involved with natural resources management in urban areas. If we look at community involvement in natural resource management in urban environments then involvement in groups that undertake bushcare and/or streamwatch/waterwatch activities is often quite extensive. A survey conducted by the SMCMA in 2009 (SMCMA, 2009) found that 7,878 volunteers worked as part of small groups that met on a regular basis and 86% of those regular volunteers were involved in bushcare. Almost 12,000 volunteers contributed time for one-off occasions at community events organised throughout 2009. This equated to around 180,196 volunteer hours with an estimated value of $6,825,840. Also in Sydney in 2009 more than 200 volunteers were monitoring waterway health at 42 different sites twice a year along the Georges River (GRCCC, 2009). Most of our major cities in Australia are also located on the coastline and have large numbers recreational fishing clubs and sailing or boating clubs as well as a commercial fishing industry. One of the things that links all these groups is their interest in (whether to protect, enhance or recreate) receiving environments for stormwater. Dahlenburg, Birtles

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Tapping into this extensive and existent network of groups and individuals provides opportunities for WSUD to promote the synergies and benefits that could occur to the receiving environments that these individuals are so committed to protecting, restoring or just using. A recent study investigated life satisfaction at the individual and neighbourhood levels in Baltimore (Vemuri, et al. 2011) and found that “higher levels of subjective environmental quality in urban communities consistently lead to higher levels of life satisfaction regardless of whether it is measured at the individual or neighboorhood scale of analysis. This finding appears to strongly support the notion that the perceived existence of and ease of access to natural surroundings has a positive impact on individual and neighboorhood satisfaction throughout the urban environment.” (Vemuri, Morgan et al. 2011 p 18).

CONCLUSIONS The early “promoter” benefits for WSUD, such as percentage or kilogram reductions of nitrogen, sediments and phosphorous and peak flow reductions have served the field well as a communication tools for professionals or actively engaged community members. It appears that relying on these and the more recent addition on reduction in the urban heat island effect may limit the prospects of WSUD being explored and incorporated into the general community’s lexicon. Limiting ourselves to explaining WSUD to the general community and/or councillors using terms and methods developed to engage professionals and institutions is unlikely to enable us to make significant progress in gaining voluntary uptake of WSUD by the community and private home owners. This will be a requirement (see Dahlenburg & Morison 2009) if we are to realise our vision of achieving truly water sensitive cities. The areas explored in more detail in this paper were urban biodiversity, human health and social capital/interaction all offer excellent “promoter” value and should be included in any list of benefits that might accrue as a result of implementing WSUD more extensively, particularly into the existing urban fabric. The community is a vast pool of individuals and groups with a wide range of professional and private interests, beliefs, hobbies and associations. It would therefore appear prudent to incorporate as many other researched benefits or “promoters”, often from seemingly unrelated fields, that can provide support for the uptake or adoption of WSUD. Our “community engagement toolkit” should try to explain or demonstrate the associations between WSUD and as many widely held interests, beliefs or hobbies of the community as possible. This could also allow for a type of 2“scaffolding” to occur between the interests and/or beliefs of individuals and WSUD and allow a deeper and more personal connection to be made with WSUD and its benefits in urban environments. Given that WSUD is the connection between or natural systems and our socially constructed systems it is recommended that a more extensive review of links between research in other areas and WSUD be undertaken as this may offer up a pool of possible research collaborations/investigations for WSUD practitioners to explore. 2

Scaffolding is an extension of one of Vygotsky’s educational psychology theories developed in the 1930’s around the zone of proximal development (see Vygotsky 1986).

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