Positioning urban rivers within urban ecology

Abstract

Rivers are important components of many urban systems, and research into urban rivers is increasing internationally, both in scope and intensity. As an introduction to a special section on urban rivers, this short article briefly highlights some key trends in urban river research based on a survey of published articles from Web of Knowledge, before summarising the contributions made by the special section papers. In particular, there has been a general increase in work on urban rivers since the 1990s, with a more dramatic increase from 2001. Most published research has concentrated on water quality and its wider environmental implications; ecologically, many studies have focused on autecology, community ecology or river restoration/rehabilitation, with the main emphasis on macroinvertebrates or fish. Geographically, most studies have taken place in North America (mainly the US) and Asia (mainly China). In the large majority of cases research has been on relatively small rivers within urbanised catchments rather than large, heavily urbanised systems within major towns or cities. Given the wide range of topics and studies relating to urban river research, a detailed meta-analysis of the urban river ecology literature would be a useful endeavour. The six papers included in the special section of this issue provide a sample of some of key and emerging themes within recent urban river research, and originate from a session on the understanding and management of urban rivers held at the Royal Geographical Society (with IBG) Annual Meeting in 2010, at Imperial College London.

Full text

Positioning urban rivers within urban ecology
Robert A. Francis
Published online: 1 March 2012
#Springer Science+Business Media, LLC 2012
Abstract Rivers are important components of many urban systems, and research into urban
rivers is increasing internationally, both in scope and intensity. As an introduction to a
special section on urban rivers, this short article briefly highlights some key trends in urban
river research based on a survey of published articles from Web of Knowledge, before
summarising the contributions made by the special section papers. In particular, there has
been a general increase in work on urban rivers since the 1990s, with a more dramatic
increase from 2001. Most published research has concentrated on water quality and its wider
environmental implications; ecologically, many studies have focused on autecology, com-
munity ecology or river restoration/rehabilitation, with the main emphasis on macroinverte-
brates or fish. Geographically, most studies have taken place in North America (mainly the
US) and Asia (mainly China). In the large majority of cases research has been on relatively
small rivers within urbanised catchments rather than large, heavily urbanised systems within
major towns or cities. Given the wide range of topics and studies relating to urban river
research, a detailed meta-analysis of the urban river ecology literature would be a useful
endeavour. The six papers included in the special section of this issue provide a sample of
some of key and emerging themes within recent urban river research, and originate from a
session on the understanding and management of urban rivers held at the Royal Geograph-
ical Society (with IBG) Annual Meeting in 2010, at Imperial College London.
Keywords Urban river .Urban stream .Urban ecology .Review .Synthesis .Freshwater
As we pass the point in history where the majority of the people on the planet live in
urban areas (UNFPA 2007), it is heartening that the scientific study of urban ecosystems
continues to gain momentum within a range of disciplines and across a broad geographical
spectrum (e.g. Forman 2008; Pickett et al. 2011a,b;Kowarik2011; Francis et al. 2012). Recent
studies have moved beyond the presentation of case studies to present increasingly broad
Urban Ecosyst (2012) 15:285–291
DOI 10.1007/s11252-012-0227-6
R. A. Francis (*)
Department of Geography, King’s College London, Strand, London WC2R 2LS, UK
e-mail: robert.francis@kcl.ac.uk

syntheses. This has helped to highlight the challenges and benefits of studying urban
systems not just for urban planning and management, but for understanding fundamental
aspects of ecosystem structure and process, resource use and metabolism, species–environment
interactions, and the explicit and intrinsic interrelationships between humans and their
environment (Grimm et al. 2008; Pickett et al. 2011a,b; Ramalho and Hobbs 2012;
Francis et al. 2012).
Urban rivers have key ecological and societal roles within broader urban systems. Indeed,
most urbanisation has historically begun at locations where key resources and services are
found, including fresh water, food, transportation links, ease of defence and waste
disposal (Grimm et al. 2008). River systems generally provide all of these, and prior
to the development of extensive and dedicated transport networks that allowed the
movement of people and goods (such as the railway and highway networks that allowed
the development of many towns and cities throughout the US; Anas et al. 1998), river
and estuarine/coastal systems were the foci for most urban development. The legacy of
this often unchecked development is widespread degradation and destruction of riverine
habitats coupled with impacts to hydrological regimes, alluvial aquifer storage, water
quality, geomorphological patterns and processes, and fluvial/riparian ecotones. Taken
as a whole, these impacts have resulted in declines in riverine ecological quality and
precipitous losses of biodiversity at both local and regional scales (Groffman et al. 2003;
Gurnell et al. 2007;Wengeretal.2009; Everard and Moggridge 2012). Nevertheless, urban
rivers continue to be important features within both the physical and cultural landscapes of
urbanised areas. Rivers are central to the identity of many towns and cities (e.g. the Thames in
London, the Seine in Paris, the Hudson in New York, the Yarra in Melbourne). Further,
waterfront areas often represent desirable areas for urban development and gentrification
(e.g. Breen and Rigby 1994; Chang and Huang 2011), and are the aquatic ecosystems
that the majority of urban populations most commonly see and reflect upon in their
daily lives (e.g. Gabr 2004).
Research interest in urban river systems began to increase notably in the early 1990s, with
a more dramatic increase from 2001 (Fig. 1). Based on a survey of articles from Web of
Knowledge using the search terms “urban stream”OR “urban river”and scrutinised
Year of
p
ublication
Number of articles
5
0
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
10
0
10
5
11
0
11
5
12
0
12
5
13
0
13
5
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
Fig. 1 Publications including the search terms “urban river*”or “urban stream*”included in Web of
Knowledge, arranged according to year published. Search conducted on 14 January 2012
286 Urban Ecosyst (2012) 15:285–291

individually, most studies have focused on water quality and its wider environmental
(including human health) implications (Fig. 2a). Other studies have focused on topics
ranging from river restoration, hydrogeomorphology, biogeochemical processes, and
autecology or community ecology/biodiversity of aquatic organisms (usually macro-
invertebrate or fish taxa; Fig. 2b). Unsurprisingly, bacteria are commonly studied, but
mainly as indicators of water quality. These results are comparable to Wenger et al.’s
(2009) review of key research questions for urban streams; though differences between
the brief literature summary presented here (Fig. 2) and Wenger et al. (2009) will
inevitably result from the different timescales reported (1988–2008 by Wenger et al.
2009, 1968–2011 here), and the search terms used. In Wenger et al.’s(2009) study, the
search terms “urban*”and “stream* OR river*”were disaggregated, meaning that rivers
and streams within a broadly urbanised catchment, or downstream of an urban area for
example, may have been included, whereas the search terms here were “urban stream
OR urban river”, potentially restricting the publications extracted to more specifically
urban foci. Nevertheless, a more complete meta-analysis or systematic review of urban
river ecology seems like a worthwhile exercise to establish the current state of knowledge in
more depth.
Fig. 2 Breakdown of a subsample of articles published in relation to urban rivers from Web of Knowledge.
In November2011, 1,184 articleswere found using the searchterms “urban river*”OR “urban stream*”.Thiswas
reduced to 753 articles for individual scrutiny by using the more restrictive terms “urban river”OR “urban
stream”. Of the 753 articles, 68 were found to be repeat or incomplete entries, leaving 685 articles for further
analysis. These were classified according to aprimary focus, borganisms studied (of which only the most
common six are presented) and cbroad geographical location (including ‘general’studies that include conceptual
or review work across geographical regions). All values are rounded to the nearest whole number
Urban Ecosyst (2012) 15:285–291 287

It is certainly clear that ecological research on urban rivers is increasing, particularly
following key advances such as the quantification of urbanization impacts and development
of the urban stream syndrome (USS) concept (Paul and Meyer 2001; Walsh et al. 2003), and
progress in rehabilitation efforts (e.g. Booth 2005). Wenger et al. (2009) identified key
research foci for urban rivers, with priorities ranging from fundamental linkages between
urbanisation and biotic response at differing scales, to the development of appropriate
ecosystem indicators and communication tools to facilitate river management and improve-
ment. There is also something of a research gap for work on major urban systems; most
ecological studies on urban rivers have focused on smaller systems within urbanised
catchments, rather than heavily urbanised and engineered rivers, in part because the
investigation of such systems can be problematic. However, some notable exceptions
include bodies of work on the River Thames through London (e.g. Attrill 1998; Francis and
Hoggart 2009,2012; Hoggart et al. 2012) and the lower Passaic River in New Jersey (e.g.
Iannuzzi et al 2005; Kinnell et al 2007;Conderetal.2009). Geographically, the large majority
of work on urban rivers has taken place in North America (mainly the US), Asia (mainly
China), and Europe (mainly western Europe) (Fig. 2c). South America (mainly Brazil),
Australia and New Zealand have fewer studies, while urban Africa is clearly under-
researched and this is likely to be a major research gap given the potential for urbanisation in
Africa (Wisner and Pelling 2008; though see Potts 2012). The low number of articles from
some parts of the world may reflect a reduced tendency for research to be published in
international English language journals, and it is likely that many more studies, particularly
from China, exist but are not included in Web of Knowledge.
Increased interest in urban rivers has in part been driven by an increasing acknowledge-
ment of the importance of such systems (both ecologically and socially), but also by the need
to comprehensively understand and manage them in order to address international legisla-
tion. An example is the EU Water Framework Directive (2000/60/EC), which requires all
European water bodies to achieve ‘good ecological status’by 2015, or in the case of heavily
modified water bodies (which includes many urbanised systems), ‘good ecological potential’
(see Borja and Elliott 2007 for further definition and discussion). Despite this, fundamental
questions remain regarding urban rivers, from what an ‘urban’river actually is (linked
perhaps to wider discussions on the definition of ‘urban’; see MacGregor-Fors 2011; Francis
and Chadwick 2012), and what their defining characteristics and range of variation might be
(e.g. Gurnell et al. 2007; Wenger et al. 2009) to how they may be rehabilitated, restored or
otherwise improved (e.g. Booth 2005; Findlay and Taylor 2006; Francis 2009; Wenger et al.
2009). There is also greater engagement with societal parameters and values in order to more
fully understand and manage urban rivers, with some recent studies in particular highlighting
the importance of the social dimension (e.g. Eden and Tunstall 2006; Lundy and Wade 2011;
Pickett et al. 2011b).
This special section results from a session dedicated to the understanding and manage-
ment of urban rivers held at the Royal Geographical Society (with IBG) Annual Meeting in
2010, at Imperial College London. The papers presented here provide a sample of some of
the key themes within recent urban river research, though necessarily only begin to touch
upon some of the unknowns (Wenger et al. 2009). The place of urban rivers with the
framework of ecosystem services is addressed by Everard and Moggridge (2012), who note
that service concepts, particularly those associated with recreation and education, are
increasingly being used to justify restoration efforts and are often reported in grey literature.
Despite this, methodologies for applying the ecosystem services framework to urban rivers
vary, for example in what may be considered an appropriate level of monetisation of
services, in comparison to non-economic stakeholder valuation. Although various tools
288 Urban Ecosyst (2012) 15:285–291

exist for ecosystem service applications, they often require a level of understanding of the
urban river context that is frequently lacking; this highlights the need for greater investiga-
tion and consideration of the processes driving such services. Everard and Moggridge (2012)
further review aspects of the application of ecosystem services to urban rivers, drawing on
examples from the UK, and conclude that where possible a holistic ecosystem approach is
perhaps the best way of unifying the different stakeholders of urban river systems.
Ramírez et al. (2012) consider urban rivers on tropical islands and how they may present
characteristics that differ from urban river generalities and the urban stream syndrome
paradigm, with a focus on Puerto Rico and Hawaii. They note in particular that tropical
island streams are often dominated by diadromous fish and shrimp species, which may
display increased tolerance to urbanisation and associated impacts due to their utilisation of
both freshwater and marine ecosystems, as long as longitudinal connectivity of the river is
maintained to facilitate movement. Consequently, although macroinvertebrates in such
systems (which are not diadromous) may respond to urban conditions as predicted by the
urban stream syndrome, fish and shrimp communities may not, further illustrating differen-
tial responses to the syndrome according to the biological assemblage and geographical
region under consideration.
Two field studies included here consider macroinvertebrates in urban rivers, but in
very different systems. Hoggart et al. (2012) look at the macroinvertebrate diversity of
flood defence walls along the heavily engineered River Thames through central London
(UK), finding that wall construction material and position relative to flow disturbance
influence the level of diversity and the biotic communities found. Chadwick et al.
(2012) examine the effects of urbanisation on headwater tributaries of the St. Johns
River in Florida (US). They find an unexpected positive relationship between urbani-
sation and macroinvertebrate richness, possibly in relation to altered flow regimes that
create intermediate disturbance conditions and thereby support a range of different
species. The research further suggests that river ecosystems may respond in a variety
of ways to urbanisation, and that further work is needed to elucidate the range and
variation of responses.
The final two papers in this special section focus on UK rivers. Cockel and Gurnell
(2012) investigate the riparian seed bank of the River Brent in London, in comparison with
several rural systems. Among other things, they find that, along with the expected reduction
in species diversity found along the urban compared to the rural systems, the Brent contains
a substantially higher proportion of alien species (21% compared to 4–5%). This further
highlights the role that urban ecosystems may play in the establishment and spread of both
terrestrial and aquatic invasive plant species; a concern also noted by Klotz and Kühn
(2010). The complex issues surrounding urban river assessment and restoration in the UK
are considered by Shuker et al. (2012), focusing on the communication of biophysical river
conditions to a range of stakeholders. They present an urban river survey toolkit and
illustrate how it may be used for concise but informative comparisons of urban river
stretches to allow for more effective decision-making, thereby supporting resource use and
management efforts.
Although these papers represent only a limited snapshot of the sort of research being
conducted in urban river systems, they help to demonstrate the range of interdisciplinary
work needed to successfully understand and manage such systems; from concept develop-
ment, refinement and validation to robust river assessment and rehabilitation techniques
applied across the ecology/society interface. With growing pressure on freshwater systems
throughout the world (e.g. Dudgeon et al. 2006; Vörösmarty et al. 2010) urban river systems
are, and will remain, an important focus for ecological research.
Urban Ecosyst (2012) 15:285–291 289

References
Anas A, Arnott R, Small KA (1998) Urban spatial structure. J Econ Lit 36:1426–1464
Attrill MJ (ed) (1998) A rehabilitated estuarine ecosystem: the environment and ecology of the Thames
estuary. Kluwer, London
Booth DB (2005) Challenges and prospects for restoring urban streams: a perspective from the Pacific
Northwest of North America. J N Am Bentholl Soc 24:724–737
Borja A, Elliott M (2007) What does ‘good ecological potential’mean, within the European Water Framework
Directive? Mar Pollut Bull 54:1559–1564
Breen A, Rigby D (1994) Waterfronts: cities reclaim their edge. McGraw Hill, New York
Chadwick MA, Thiele JE, Huryn AD, Benke AC, Dobberfuhl DR (2012) Effects of urbanization on
macroinvertebrates in tributaries of the St. Johns River, Florida, USA. Urban Ecosyst (this issue).
doi:10.1007/s11252-011-0217-0
Chang TC, Huang S (2011) Reclaiming the city: waterfront development in Singapore. Urban Stud
48:2085–2100
Cockel CP, Gurnell AM (2012) An investigation of the composition of the urban riparian soil propagule bank
along the River Brent, Greater London, UK, in comparison with previous propagule bank studies in rural
areas. Urban Ecosyst (this issue). doi:10.1007/s11252-011-0203-6
Conder JM, Sorensen MT, Leitman P, Martello LB, Wenning RJ (2009) Avian ecological risk potential
in an urbanized estuary: Lower Hackensack River, New Jersey, USA. Sci Total Environ 407:1035–
1047
Dudgeon D, Arthington AH, Gessner MO, Kawabata ZI, Knowler DJ, Leveque C, Naiman RJ, Prieur-Richard
AH, Soto D, Stiassny MLJ, Sullivan CA (2006) Freshwater biodiversity: importance, threats, status and
conservation challenges. Biol Rev 81:163–182
Eden S, Tunstall S (2006) Ecological versus social restoration? How urban ri ver restoration chall enges
but also fails to challenge the science-policy nexus in the Un ited Kingdom. Environ Plann C
24:661–680
Everard M, Moggridge HL (2012) Rediscovering the value of urban rivers. Urban Ecosyst (this issue).
doi:10.1007/s11252-011-0174-7
Findlay SJ, Taylor MP (2006) Why rehabilitate urban river systems? Area 38:312–25
Forman RTT (2008) Urban regions: ecology and planning beyond the city. Cambridge University Press,
Cambridge
Francis RA (2009) Perspectives on the potential for reconciliation ecology in urban riverscapes. CAB
Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources 4, art 73:1–20
Francis RA, Chadwick MA (2012) What makes a species synurbic? Appl Geogr 32:514–552
Francis RA, Hoggart SPG (2009) Urban river wall habitat and vegetation: observations from the River
Thames through central London. Urban Ecosyst 12:468–485
Francis RA, Hoggart SPG (2012) The flora of urban river wallscapes. River Res Appl. doi:10.1002/rra.1497
Francis RA, Lorimer J, Raco M (2012) Urban ecosystems as ‘natural’homes for biogeographical boundary
crossings. Trans Inst Br Geogr. doi:10.1111/j.1475-5661.2011.00470.x
Gabr HS (2004) Perception of urban waterfront aesthetics along the Nile in Cairo, Egypt. Coast Manag
32:155–171
Grimm NB, Faeth SH, Golubiewski NE, Redman CL, Wu JG, Bai XM, Briggs JM (2008) Global change and
the ecology of cities. Science 319:756–760
Groffman PM, Bain DJ, Band LE, Belt KT, Brush GS, Grove JM, Pouyat RV, Yesilonis IC, Zipperer WC
(2003) Down by the riverside: urban riparian ecology. Front Ecol Environ 1:315–321
Gurnell A, Lee M, Souch C (2007) Urban rivers: hydrology, geomorphology, ecology and opportunities for
change. Geogr Compass 1:1118–1137
Hoggart SPG, Francis RA, Chadwick MA (2012) Macroinvertebrate richness on flood defence walls of the
tidal River Thames. Urban Ecosyst (this issue). doi:10.1007/s11252-011-0221-4
Iannuzzi TJ, Armstrong TN, Thelen JB, Ludwig DF, Firstenberg CE (2005) Characterization of chemical
contamination in shallow-water estuarine habitats of an industrialized river. Part 1: organic compounds.
Soil Sediment Contam 14:13–33
Kinnell JC, Bingham MF, Hastings EA, Ray R, Craven V, Freeman M (2007) A survey methodology for
collecting fish consumption data in urban and industrial water bodies (Part 1). J Toxicol Environ Health
Part A Curr Issues 70:477–495
Klotz S, Kühn I (2010) Urbanisation and alien invasion. In: Gaston KJ (ed) Urban ecology. Cambridge
University Press, Cambridge, pp 120–133
Kowarik I (2011) Novel urban ecosystems, biodiversity, and conservation. Environ Pollut 159:1974–1983
290 Urban Ecosyst (2012) 15:285–291

Lundy L, Wade R (2011) Integrating sciences to sustain urban ecosystem services. Prog Phys Geog
35:653–669
MacGregor-Fors I (2011) Misconceptions or misunderstandings? On the standardization of basic terms and
definitions in urban ecology. Landscape Urban Plan 100:347–349
Paul MJ, Meyer JL (2001) Streams in the urban landscape. Annu Rev Ecol Syst 32:333–365
Pickett STA, Cadenasso ML, Grove JM, Boone CG, Groffman PM, Irwin E, Kaushal SS, Marshall V,
McGrath BP, Nilon CH, Pouyat RV, Szlavecz K, Troy A, Warren P (2011a) Urban ecological systems:
scientific foundations and a decade of progress. J Environ Manage 92:331–362
Pickett STA, Buckley GL, Kaushal SS, Williams Y (2011b) Social-ecological science in the humane
metropolis. Urban Ecosyst 14:319–339
Potts D (2012) What do we know about urbanisation in sub-Saharan Africa and does it matter? Int Dev Plan
Rev 34. doi:10.3828/idpr.2012.1
Ramalho CE, Hobbs RJ (2012) Time for a change: dynamic urban ecology. Trends Ecol Evol. doi:10.1016/j.
tree.2011.10.008
Ramírez A, Engman A, Rosas KG, Perez-Reyes O, Martinó-Cardona DM (2012) Urban impacts on tropical
island streams: some key aspects influencing ecosystem response. Urban Ecosyst (this issue).
doi:10.1007/s11252-011-0214-3
Shuker L, Gurnell AM, Raco M (2012) Some simple tools for communicating the biophysical condition of
urban rivers to support decision making in relation to river restoration. Urban Ecosyst (this issue).
doi:10.1007/s11252-011-0207-2
United Nations Population Fund (UNFPA) (2007) Urbanization: A majority in cities. UNFPA, available at
www.unfpa.org/pds/urbanization.htm [accessed 26 November 2011]
Vörösmarty CJ, McIntyre PB, Gessner MO, Dudgeon D, Prusevich A, Green P, Glidden S, Bunn SE,
Sullivan CA, Liermann CR, Davies PM (2010) Global threats to human water security and river
biodiversity. Nature 467:555–561
Walsh CJ, Roy AH, Feminella JW, Cottingham PD, Groffman PM, Morgan RP (2003) The urban stream
syndrome: current knowledge and the search for a cure. J N Am Bentholl Soc 24:706–723
Wenger SJ, Roy AH, Jackson CR, Bernhardt ES, Carter TL, Filoso S, Gibson CA, Hession WC, Kaushal SS,
Marti E, Meyer JL, Palmer MA, Paul MJ, Purcell AH, Ramirez A, Rosemond AD, Schofield KA,
Sudduth EB, Walsh CJ (2009) Twenty-six key research questions in urban stream ecology: an assessment
of the state of the science. J N Am Bentholl Soc 28:1080–1098
Wisner B, Pelling M (2008) African cities of hope and risk. In: Pelling M, Wisner B (eds) Disaster risk
reduction: cases from urban Africa. Earthscan, London, pp 17–42
Urban Ecosyst (2012) 15:285–291 291