Urban Disturbance Ecology

Brendan Kempf

MIA LEHRER + ASSOCIATES, LOS ANGELES

 

EMERGENT RESPONSES TO NATURAL DISTURBANCE REGIMES AND URABN RESILIENCE

 

ABSTRACT

Conceptualising a city as an ecosystem, particularly an urban ecosystem, provides opportunities for exploring how the application of ecological processes and paradigms can inform our understanding of the interconnected and interdependent aspects of the city. 

Contemporary ecological thinking is beginning to embrace the notion that complex, interdependent emergent systems cannot be fully understood from just one perspective. Instead, such systems need to be considered from different perspectives, with each informing the others, and ultimately contributing to a holistic and interrelated understanding of the system. As such, this essay does not attempt to develop an all-encompassing view of the city as an ecosystem, but rather to focus on how cities respond to disturbance of natural phenomena. 

In particular, this paper will explore the emergent logics of the infrastructural response of Los Angeles to its problematic river, ad-hoc interventions in Christchurch following the devastating earthquakes, and a speculative proposal for how disturbance might be a model for urbanism in Pacific island states. 

Cultivating Fire Annuals Successional Design Concept

Cultivating Fire Annuals Successional Design Concept

THEORETICAL APPROACH: ECOSYSTEM THEORY & COMPLEX SYSTEMS

Traditionally, ecosystems were conceived of simple linear systems that would eventually reach a stable climax condition. Once that stable climax condition was reached, the ecosystem would then maintain itself in a static condition indefinitely. Recently however, ecologists have begun to recognise that natural systems are always in a state of flux – constantly shifting and adapting to environmental changes. Major changes in environmental conditions that cause flux to occur are referred to as disturbance. Resilience refers to an ecosystem’s ability to recover from and adapt to disturbance; when the same kind of disturbance affects an ecosystem on a regular basis, it is called a disturbance regime and the ecosystem in question is typically adapted to that disturbance. 

For instance, many grassland ecosystems are adapted to fire disturbance regimes, typically from stray lightning strikes. Fire-adapted grasses burn quickly and have a root system that allows them to survive and quickly regenerate quickly after the fire, even in low temperatures. Whilst any tree saplings that are not fire adapted, burn and perish even in lower temperate fires. This negates the growth of saplings into mature trees that would eventually shade out the grasses and in turn transition the plant community into a woodland. The fire regime and grass adaptations are even further interdependent, where the burning of the plant material recycles the plant nutrients back into the soil that plants use to regrow after the disturbance. On an even larger scale, one can see how fire regime adapted plant communities are spatially located based on macro-level climate patterns and weather events. 

This simplistic example of grassland fire ecology, reveals how there are multiple interdependent layers of interactions that reveal different aspects of how the grassland ecosystem functions and adapts. Within the last decade the field of ecology has begun to embrace the idea that “each perspective on an ecosystem reveals only one face to its complex and changing states.” (1) For instance, if one studied the grassland from the perspective of nutrient cycles the critical role of fire in suppressing the growth of trees might be missed. This idea proposes a holistic and inherently interdisciplinary approach to understanding the complex and interdependent systems in the world; and is especially crucial for understanding the emergent properties of the city as an urban ecosystem.

If the city is conceived of as an urban ecosystem, then the effects human culture and activity have must be taken into account; which by extension includes the role of social and economic factors in human decision-making. In the same way contemporary ecologists advocate for multi-perspectival studies on the environment, the same must be done when considering the city from other disciplines. Such as anthropology, where Arjun Appadurai suggests through his five scapes, ethnoscapes, technoscapes, finanscapes, mediascapes, and ideoscapes, one might study modern, urban and globalized cultures. (2) Appadurai proposed that culture, technology, wealth and financial exchange, communication, and politics are all deeply interrelated and must all be accounted for when studying human culture. It is essential to take advantage of the perspectives offered by various disciples, as within each discipline there are definite vantage points; as suggested through Appadurai’s anthropological scapes and the multitude of ecological lenses with which one can explore interactions in an ecosystem. Therefore, this paper does not attempt to develop an all-encompassing view of the city as an ecosystem, but rather to focus on how cities respond to and are informed by disturbance regimes of natural phenomena. 

 

THE URBAN ECOSYSTEM

In its most basic form an ecosystem is a spatially defined unit in which living organisms interact with the physical world and each other, resulting in exchanges of energy, nutrients and raw materials. (3) Cities just like any other ecosystem can be defined spatially and the fact they rely on constant flows and cycles of energy, raw materials, nutrients, wealth, labour, and population. (4) The urban ecosystem is an anthropogenic ecosystem; it is unique in the disproportionate role that one species, human beings, play in affecting the outcomes of natural and artificial processes. Humans reshape the physical environment to suit their own needs, much like a beaver damming a stream, except on a much larger scale. The complex social structures and networks that humans make play a major role in how a city is formed. 

The urban ecosystem is also unique because it effectively has no discrete spatial boundaries. While the form of a city itself can be spatially defined, the flows of energy, nutrients and raw materials extend far beyond the extents of the city. A typical ecosystem is limited in terms of resource availability, serving as a limiting factor to keep populations in check. Human communication and transportation technology however, have made it possible for the massive global exchange and redistribution of not only the basic ecological needs of the city, but also wealth, fuel, manufactured goods and people. As a result an urban ecosystem is “no longer able to regulate human population size, structure, or genetic diversity.” (5) Instead, a city’s trade connections and wealth play a large role in determining its available resources, implicating economics and technology as important facets of the urban ecosystem. Social aspects of an urban ecosystem can also drive disturbance; gentrification for instance, is a culturally generated disruption that can affect the form of the city. Gentrification typically implies the displacement of a usually lower income group by a higher one. (6) Income inequalities and individual human ambitions among other factors can cause cultural-based disturbance and flux in the urban ecosystem. 

 

DISTURBANCE REGIMES OF NATURAL PHENOMENA

Transformative natural disasters, such as earthquakes, volcanism, tornadoes and sudden violent weather events such as hurricanes “are unique for urban environments as a large amount of vacant land presents itself in a very short period of time.” (7) These kinds of disturbances whilst unpredictable are known hazards, as they tend to occur over and over again within the same region. Earthquakes occur along fault lines and zones of tectonic activity; consequently, communities located in seismically active areas are aware of the high likelihood of seismic events. This is very different from the social and economic processes, such as gentrification that take longer to manifest in the urban fabric. In ecological terms a sudden natural disaster creates new spatial and potentially programmatic niches in the city. 

Other forms of disturbance such as seasonal rains, monsoons, flooding and tidal inundation occur on a regular predictable cycle and occupy the city for extended periods of time. Unlike transformative disturbance these temporal disturbances transform the character of a city for a period of time before retreating and allowing the city to return to its normal conditions; such cities lead dual lives, based on the seasons.

Chaparral: Post-Fire Succession

Chaparral: Post-Fire Succession

Disturbance- Free Trajectory

Disturbance- Free Trajectory

CHRISTCHURCH: TRANSFORMATIVE EARTHQUAKE

Between September 2010 and February 2011 the city of Christchurch (New Zealand), experienced two massive earthquakes and countless aftershocks that permanently altered Christchurch’s urban form and ecosystem. New Zealand is a seismically active region where earthquakes are a known hazard throughout the nation. The Canterbury quake on September 4th 2010 however, was not only the strongest earthquake to strike New Zealand in almost 80 years, but also occurred along a previously unknown fault line. (8) The 7.1 magnitude quake produced a visible 25 kilometre long ‘rip’ across the Christchurch region, “displacing farm paddocks and roads by as much as 4 meters.” (9) This was followed four and a half months later by a 6.3 magnitude aftershock. The following year there were over 8,500 aftershocks, with an average of 23 aftershocks per day. (10) 

As is typical for sudden intense disturbance regimes, the Canterbury Quake and Christchurch Aftershock completely altered the city of Christchurch in seconds, opening up new spatial niches throughout the city. Both earthquakes destroyed built structures and caused significant soil liquefaction that forced countless buildings to be condemned and slated for demolition. Many areas cannot be rebuilt upon because the soil liquefaction has made the ground unstable and has compromised its load bearing ability. (11) At least 50% of Christchurch’s central business district is slated for demolition. (12) The rebuilding process for Christchurch is expected to take at least two decades and the long-term planning efforts for the re-imagining of the city have only just begun. 

Even after the first earthquake in 2010 local residents began to look for ways to occupy the new spatial niches of destroyed buildings and unbuildable lots. Several different activist groups emerged with the goal of making something useful and positive out of the piles of rubble that “had appeared or were likely to appear over the coming weeks”. (13) After the second major earthquake that caused further damage and liquefaction in areas, these proposals gained even more traction. Proposed uses for the new spaces ranged from small landscaping and parklet type improvements, to public art interventions. (14)

The longevity of such interventions varied depending upon site-specific conditions. For instance, a landscaping feature added to a demolished site is likely to be temporary, as the owners will probably wish to rebuild at a later date. (15) Still, such interventions improve the quality of life in the city, at least temporarily in the wake of a natural disaster. Other areas with liquefied soils will never be rebuilt and any interventions done in such areas will be longer lasting and potentially inform a new network of open spaces throughout the city. However, it is only two years into the rebuilding process, far too early to say how the areas unsuitable for building will be reintegrated into the city. It is important to note that while new landscaping projects contribute to new ecological systems, these emergent temporary and semi-permanent interventions into the disaster spaces of the city are filling a programmatic niche and providing new uses for unused spaces. They are driven by human values and interests in improving the quality of life, soon after disturbance.

 

LOS ANGELES: INFRUSTRUCTURAL RESPONSE

While earthquakes have always been a fact of life in the Los Angeles region, the seasonal flooding of Los Angeles River was once an incredibly destructive and transformative disturbance regime before it was channelized in the 1930s. Today, the Los Angeles River is effectively a massive stormwater channel that is meant to convey as much water as possible, as quickly as possible, out of the city and into the ocean. (16) Historically the river had no consistent watercourse, meaning major storms with heavy rainfall would result in the river flowing over its banks and flooding the surrounding areas, often carving out an entirely new channel. At one time the river emptied into the Santa Monica Bay and records indicate that river dramatically shifted its course at least nine times in the 1800s. (17) Ever since Los Angeles was founded as a pueblo (native american village) in 1781 the Los Angeles River and its destructive floods have always played an integral role in the development of the city. Just a decade after the founding of the pueblo a major flood prompted the pueblo to relocate to higher ground. (18)

The disturbance caused by the river was incompatible with Los Angeles’ urban expansion and growing role in commerce. The temporary flooding and resulting damages posed a serious risk to people, property, agriculture, and the railroads; many of which were located along the river’s course and were an essential element of commerce. Even more dangerous to the city was the river’s habit of completely transforming its own watercourse. While annual rainfall patterns in Southern California do occur fairly consistently, the actual intensity of each rain event can vary significantly between years, making flood risks unpredictable. Even as early as 1874 people were recognising a need for a flood control system for the city, as noted by a road engineer in his field notes. (19) Four decades later in 1914 the Los Angeles River flood had caused extensive damage, prompting the creation of a flood control program for the city. (20) The river continued to flood and along with it the importance and power of the city’s flood control program grew. After two more devastating floods in the early 1930s the US government stepped in to take control of the flood control program and embarked on a massive infrastructural solution to all but eliminate the river’s disturbance regime: a fifty-one mile long concrete channel.

The result was a fifty-one mile long series of “vertical, trapezoidal, and transition structures” that appear as a concrete scar bisecting Los Angeles. (21) The river’s disturbance regime proved to be incompatible with the anthropogenic elements of Los Angeles’ urban ecosystem, which was to create a massive infrastructure to suppress what would otherwise be a natural form of disturbance. In fact the act of channelizing the river could be considered its own form of disturbance that virtually eradicated the river’s riparian ecosystems. Yet as testament to the resilience of the city’s urban ecosystem, new unique ecologies have emerged from the river’s present condition. Bridge overhangs provide habitat for bats and swallows; both species that are invaluable for consuming insects for urban disease control. (22) The nutrient-rich tertiary-treated sewage that makes up roughly 60% of the river’s daily flow contributes to expansive sludge and algae flats at the mouth of the river that are a valuable stopover point for migratory birds. (23) While the infrastructural solution for Los Angeles was to eliminate the river’s disturbance regime, Los Angeles’ urban ecosystem has demonstrated its ability to adapt to novel conditions and be resilient.

 

SPECULATIVE URBANISM: DISTURBANISM IN THE SOUTH PACIFIC

The anthropogenic aspect of the urban ecosystem has typically been concerned with human needs and desires such as food supply, housing, sanitation, and commerce. Natural disturbance regimes are instead disruptions to human ambitions. If disturbance was leveraged as an integral component to the city, cities might look very different. For instance, Los Angeles might not have developed with major industrial and commercial activities taking place in a river’s flood plain, or housing developments creeping further and further into fire-prone areas.

A speculative alternative form of the urban ecosystem might embrace and incorporate disturbance regimes, rather than react to them. Disturbanism, a phrase coined by Barnett and Margetts in their essay ‘Disturbanism in the South Pacific’ proposes incorporating natural disturbance regimes into the way cities are built and improve urban resilience. (24) Barnett and Margetts use islands in the Pacific as the basis for their proposal because climactic patterns result in relatively frequent and major storm events, cyclones, which are the primary natural disturbance regime. (25) Cyclones can devastate both urban ecosystems and natural (non-anthropogenic) ecosystems on the islands. However, the natural ecosystems have adapted to the disturbance and are able to recover quickly, whereas the built urban ecosystem takes longer to recover, in part due to social and economic issues such as funding, international assistance and the availability of heavy machinery. (26) Presently “instead of seeing cyclones as a necessary part of the system and therefore to be assimilated, modern urban settlement planning the Pacific attempts to resist cyclonic events.”

Barnett and Margett’s disturbanism proposal lays the theoretical argument for seamlessly weaving disturbance into the urban ecosystem without making any formal speculations on what such a design would look like. The ideas of Landscape Urbanism and Ecological Urbanism promote the use of natural ecological processes as ways of improving both the sustainability and liveability of the urban ecosystem. (27) As ecologically sound principles continue to be incorporated into design it is possible that disturbance-based flux and disturbance regimes will become integrated with the creation of the urban ecosystem, rather than problems to be reacted to. Such a model for the urban environment would be practical for a host of different reasons, not in the least of which is in an economic sense; as a city that is properly adapted to disturbance regimes will not need constant rebuilding and reinvestment every time a disturbance occurs. The impacts on residents could be minimised and presumably there would be fewer injuries and fatalities stemming from disturbance. Figuring out how to embrace and integrate disturbance-based flux into the city would make for a safer, more effective, practical and holistic city. 

Coastal Sage Scrub: Annual Flux Cycle

Coastal Sage Scrub: Annual Flux Cycle

Some forms of disturbance such as the Los Angeles River’s flood behaviour can be more or less controlled by massive infrastructural interventions; other examples of this would be the massive storm surge barriers that are being proposed for the Venice lagoon, that are currently functioning in Holland. But these kinds of infrastructural interventions are costly and are often complicit in environmental degradation. The kind of ad-hoc responses typified by the small scale, temporary interventions in Christchurch demonstrate the capacity for resilient social responses that take advantage of newly created niches in the city. Yet the optimistic hope of considering the city in terms of the response to disturbance regimes is that one-day cities might actively incorporate disturbance regimes and their responses to create more resilient cities, as Barnett and Margett theorise.


Legend For Diagrams

Legend For Diagrams


FOOTNOTES

(1) James Kay, “Framing the Situation: Developing a System Description,” in The Ecosystem Approach: Complexity,
 Uncertainty , and Managing for Sustainability, ed. David Waltner - Toews, James Kay, and Nina - Marie ELister ( N e w York: Columbia University Press, 2008); Rod Barnett, Emergence in Landscape Architecture (Oxon: Routledge, 2013), 4. 

(2) Arjun Appadurai, “Disjuncture and Difference in the Global Cultural Economy,” Communication Theories 4 (2006). 

(3) Richard T. T Forman, Land Mosaics: The Ecology of Landscapes and Regions (Cambridge [England]; New York: Cambridge University Press, 1995). 

(4) J. Morgan Grove and William R. Burch, “A Social Ecology Approach and Applications of Urban Ecosystem and Landscape Analyses: a Case Study of Baltimore, Maryland,” Urban Ecosystems 1, no. 4 (December 1, 1997): 259–275, doi:10.1023/A:1018591931544. 

(5) J. Morgan Grove, Karen E. Hinson, and Robert J. Northrop, “A Social Ecology Approach to Understanding; Urban Ecosvsterns and Landscapes,” in Understanding Urban Ecosystems: A New Frontier for Science and Education (New York: Springer, 2003), 167 – 186, www.nrs.fs.fed.us/pubs/jrnl/2003/ne_2003_grove_001.pdf. 

(6) John McDonagh, “The Christchurch Earthquakes Impact on Inner City ‘colonisers’” (January 2012), http://researcharchive.lincoln.ac.nz/handle/10182/4914. 

(7) William Syben, “Making Use of Vacant Urban Space: A Study of Christchurch after the Earthquakes of 2010/11” (University of Canterbury, 2012), 9, http://www.geog.canterbury.ac.nz/postgrad/420papers/2012/W_Syben_Geography_420_Research_Dissertation %5B1%5D.pdf. 

(8) Neil Challenger, “From the City That Rocks, Observations from Post-earthquake Christchurch New Zealand” (November 2010), http://researcharchive.lincoln.ac.nz/handle/10182/4213. 

(9) Ibid.

(10) Justin Morgenroth and Tony Armstrong, “The Impact of Significant Earthquakes on Christchurch, New Zealand’s Urban Forest,” Urban Forestry & Urban Greening 11, no. 4 (2012): 383–389, doi:10.1016/j.ufug.2012.06.003.

(11) Challenger, “From the City That Rocks, Observations from Post-earthquake Christchurch New Zealand”; Morgenroth and Armstrong, “The Impact of Significant Earthquakes on Christchurch, New Zealand’s Urban Forest.” 

(12) Roy Montgomery, “Greening the Rubble in Christchurch: Civic Ecological Reclamation Efforts During a Crisis Event,” Lincoln Planning Review 3, no. 3 (March 2012): 3–13. 

(13) Ibid.; Challenger, “From the City That Rocks, Observations from Post-earthquake Christchurch New Zealand.” 

(14) Montgomery, “Greening the Rubble in Christchurch: Civic Ecological Reclamation Efforts During a Crisis Event.”

(15) Ibid. 

(16) Blake Gumprecht, The Los Angeles River : Its Life, Death, and Possible Rebirth (Baltimore: Johns Hopkins University Press, 1999), 127. 

(17) Ibid., 137. 

(18) Ibid., 138. 

(19) Ibid., 175. 

(20) Ibid., 173.

(21) David Fletcher, “Flood Control Freakology,” in The Infrastructural City: Networked Ecologies in Los Angeles, by Kazys Varnelis (Barcelona; New York; [Los Angeles]; [New York]: Actar ; The Los Angeles Forum for Architecture and Urban Design ; The Network Architecture Lab, Graduate School of Architecture, Planning and Preservation, Columbia University, 2008). 

(22) Ibid., 44.

(23) Ibid. 

(24) Rod Barnett and Jacqueline Margetts, “Disturbanism in the South Pacific: Disturbance Ecology as a Basis for Urban Resilience in Small Island States,” in Resilience in Ecology and Urban Design,ed.S.T.A. Pickett,M.L. Cadenasso, and Brian McGrath,Future City 3 (Springer Netherlands, 2013), 443–459, http://link.springer.com.libproxy.usc.edu/chapter/10.1007/978-94-007-5341-9_27. 

(25) Ibid.

(26) Ibid., 448. 

(27) Charles Waldheim, The Landscape Urbanism Reader (New York: Princeton Architectural Press, 2006); Mohsen Mostafavi et al., Ecological Urbanism (Baden, Switzerland: Lars Müller Publishers, 2010).

 

BIBLIOGRAPHY

Appadurai, Arjun. “Disjuncture and Difference in the Global Cultural Economy.” Communication Theories 4 (2006).

Barnett, Rod. Emergence in Landscape Architecture. Oxon: Routledge, 2013.

Barnett, Rod, and Jacqueline Margetts. “Disturbanism in the South Pacific: Disturbance Ecology as a Basis for Urban Resilience in Small Island States.” In Resilience in Ecology and Urban Design, edited by S. T. A. Pickett, M. L. Cadenasso, and Brian McGrath, 443–459. Future City 3. Springer Netherlands, 2013. http://link.springer.com.libproxy.usc.edu/chapter/10.1007/978-94-007-5341-9_27.

Challenger, Neil. “From the City That Rocks, Observations from Post-earthquake Christchurch New Zealand” (November 2010). http://researcharchive.lincoln.ac.nz/handle/10182/4213.

Fletcher, David. “Flood Control Freakology.” In The Infrastructural City: Networked Ecologies in Los Angeles, by Kazys Varnelis. Barcelona; New York; [Los Angeles]; [New York]: Actar ; The Los Angeles Forum for Architecture and Urban Design ; The Network Architecture Lab, Graduate School of Architecture, Planning and Preservation, Columbia University, 2008.

Forman, Richard T. T. Land Mosaics: The Ecology of Landscapes and Regions. Cambridge [England]; New York: Cambridge University Press, 1995.

Grove, J. Morgan, and William R. Burch. “A Social Ecology Approach and Applications of Urban Ecosystem and Landscape Analyses: a Case Study of Baltimore, Maryland.” Urban Ecosystems 1, no. 4 (December 1, 1997): 259–275. doi:10.1023/A:1018591931544.

Grove, J. Morgan, Karen E. Hinson, and Robert J. Northrop. “A Social Ecology Approach to Understanding; Urban Ecosvsterns and Landscapes.” In Understanding Urban Ecosystems: A New Frontier for Science and Education, 167 – 186. New York: Springer, 2003. www.nrs.fs.fed.us/pubs/jrnl/2003/ne_2003_grove_001.pdf.

Gumprecht, Blake. The Los Angeles River : Its Life, Death, and Possible Rebirth. Baltimore: Johns Hopkins University Press, 1999.

Kay, James. “Framing the Situation: Developing a System Description.” In The Ecosystem Approach: Complexity, Uncertainty, and Managing for Sustainability, edited by David Waltner-Toews, James Kay, and Nina-Marie E Lister. New York: Columbia University Press, 2008.

McDonagh, John. “The Christchurch Earthquakes Impact on Inner City ‘colonisers’” (January 2012). http://researcharchive.lincoln.ac.nz/handle/10182/4914.

Montgomery, Roy. “Greening the Rubble in Christchurch: Civic Ecological Reclamation Efforts During a Crisis Event.” Lincoln Planning Review 3, no. 3 (March 2012): 3–13.

Morgenroth, Justin, and Tony Armstrong. “The Impact of Significant Earthquakes on Christchurch, New Zealand’s Urban Forest.” Urban Forestry & Urban Greening 11, no. 4 (2012): 383–389. doi:10.1016/j.ufug.2012.06.003.

Mostafavi, Mohsen, Gareth Doherty, Harvard University, and Graduate School of Design. Ecological Urbanism. Baden, Switzerland: Lars Müller Publishers, 2010.

Syben, William. “Making Use of Vacant Urban Space: A Study of Christchurch after the Earthquakes of 2010/11.” University of Canterbury, 2012. http://www.geog.canterbury.ac.nz/postgrad/420papers/2012/W_Syben_Geography_420_Research_Dissertation%5B1%5D.pdf.

Waldheim, Charles. The Landscape Urbanism Reader. New York: Princeton Architectural Press, 2006.