Book Review: Drosscape by Alan Berger

Author Alan Berger, professor of urban design at MIT, takes an in-depth look at the leftover pieces of land in urban centers. Borrowed from Lars Lerup’s essay entitled “Stim & Dross,” dross refers to waste landscapes, the leftovers between developed lands. Berger calls this the in-between’s of a city’s urban fabric. He makes the case that urban lands are in constant flux and that urban sprawl is rampant, and will continue to do so even with the best of urban planning intentions. As business move out of the developed cores, obsolete lands form in the center, which spreads outward like a cancer. Lerup proposes that urban areas could intentionally provide a mix of developed and leftover lands, a hybridization of use and non-use. This is a refreshing concept and flies in the face of current urban planning, which seeks to place priority on infilling vacant lands (brownfields and greyfields) for new development. The idea is that infill curbs sprawl and perhaps maintain more forests and fields at the city edges. One problem with this idea is that unless there is an urban growth boundary (such as found in Portland, OR), infill doesn’t seem to hinder eventual sprawl. Something will build there eventually. The other, more insidious aspect, is that with an attitude of continual infill, few open green spaces are left within the city. Albert Pope, professor of architecture at Rice University, argues against filling in these voids. Continual infill results in communities like Roseville, Michigan; the city of my childhood that had no parks or open areas (other than athletic fields) within walking or biking distance—just wall to wall hardscape. Of course now with the demise of Detroit, the industrial edges of the city are becoming forested once again. Hopefully they will keep a few of these before they renew, redevelop, and infill. Berger takes a look at 10 urbanized areas in the book, ranging from Atlanta to Phoenix, and reveals the drosscapes found there, both in map form and aerial photos. Drosscapes presents a graphically intriguing overview of leftover lands in cities within an urban planning context. It provides some new terms for places that have no words—such as “demalling” (obsolete shopping mall areas) and “terrain vague” (economically failing areas). It also looks at cities at the metascale, providing a big picture view. But it also offers incentive to the architect, designer, or landscape architect at the project scale, to design “empty areas” within the property footprint—whether these be forested or reclaimed lands that remain unbuilt, or unpurposeful. What could these look like?

Wildlife Types Vary According to Urban Density

Cities tend to have similar wildlife types and habitats, no matter where you may live in the world. That’s why Norway rats, cockroaches, and pigeons are everywhere—they follow in our footsteps. But research has shown that native plants and wildlife are plentiful at the city edges but decrease as they get closer to downtown. Michael McKinney from the University of Tennessee sums this up nicely in his 2006 article in the journal of Biological Conservation. Entitled Urbanization as a major cause of biotic homogenization, McKinney collects a wealth of data from around the world, as well as mining existing data sets, on how wildlife and plants respond to urban density. He observes that cities tend to share similar wildlife types and habitat structures and thus are very homogenized (similar) and homeostatic (unchanging). Whereas city edges that abut natural conditions tend to be more varied and dynamic thus providing more habitat types and food for urbanophobes (wildlife that do not like being around humans and their environments). Based on the information and references McKinney provides in his article, I observed that there are three primary and distinct urban habitat zones—periurban, suburban, and urban. Or, in other words, the farther that one gets from the wildland interface and the denser the development, that wildlife and habitats change. This may be useful information to landscape architects or planners that seek to provide green spaces for wildlife habitat in densely urban areas.  The types of wildlife that you hope to attract probably depends upon the scale of habitat that you are designing and how they will arrive from native populations. The following graphic that I developed summarizes the general wildlife and habitat characteristics as provided by McKinney (2006):

It’s been noted that urban areas may exhibit a high diversity of plants and animals, sometimes more than the adjoining countryside. But while the numbers may be high due to more planted exotic vegetation species; the quality of the habitats, food, and ecosystem services may actually be more impoverished as compared to a native landscape. This is mostly due to the use of plants (native or exotic) with a reduced gene pool and a lack of resilience. McKinney notes that using local native plant species in urban areas enriches not only the urban genepool, but creates a much richer environment for people.

Somewhere in Starkville

Melbourne, Australia: The City Within a Forest

The “City of Melbourne is driving an ecosystem-based climate adaptation program with a goal to double urban forest canopy cover and increase permeability to cool the city’s summertime temperatures by 4°C. This presentation video reflects on how the City of Melbourne is implementing a transformative program of works to create climate resilient urban landscapes that support healthy ecosystems and healthy communities. In particular, it focuses on the role of citizen participation and transparency in co-designing plans to turn the world’s most liveable city into a city within a forest.” Learn more about this project in a video presentation by Yvonne Lynch, City of Melbourne Urban Ecology and Forest team, at the Biophilic Cities Project Youtube channel at https://www.youtube.com/watch?v=W6tpNXXUmow  (40 minutes).

More parks and green spaces in urban areas equals more bird species

 Northern flicker

A 2003 study published in Conservation Ecology has determined that more bird species are found in urban areas with parks and natural features than in more densely developed areas. The study by Melles, Glenn and Martin collected data at 285 stations in Vancouver and Burnaby, British Columbia, Canada. The authors counted the number of bird species present and noted the types of land uses around their sampling sites. In particular, they found that certain landscape features such as freshwater streams, large trees, and berry producing shrubs were correlated with the number of bird species. They conclude that parks and green areas should be integrated into city planning and development to enhance bird diversity. Housing developments adjacent green reserves should “minimize impervious surface cover (concrete, roofs and asphalt), minimize house size, maintain native tree cover and berry shrubs, integrate new ponds, and maintain and develop natural freshwater sources into planning designs.”

How old is your landscape?

 

Youthful landscape

Is it better to manage your landscape as an older woodland model or as a younger and youthful grassland? It depends. The context of what the property has on it and what is around it are important factors. But if it is biodiversity that you are after, then periodic disturbances might be your answer. Something called the “intermediate disturbance hypothesis” by Connell (1978) states that heavily impacted landscapes (regularly mown or burned) and undisturbed landscapes (older mature forest) results in less species richness. 

 

Medium aged forest

But those in-between aged forests, not too young and not too old (“overmature”), tends to have the most species present. This has been documented for birds (Jokimaki and Suhonen 1993) and butterflies (Blair and Launer 1997), but obviously this is not the case for all animal types. So to increase biodiversity on your property it may be advantageous to reduce the amount of lawn and convert it to woodland plants, while in a heavily wooded landscape it may be useful to thin the canopy branches or remove a few trees to open it to more sunlight. But then again, it depends.

Older woodland

49 Farms, San Francisco

I first saw Jay 'Blue Tape' Rosenberg a few years ago at Hayes Valley Farm in San Francisco. This urban permaculture garden had fat green squash plants interspersed with fava beans, marigolds, and rampant tomatoes. The garden was built upon the rubble of an abandoned interstate exit and yet it thrived with plants. 

 Jay Rosenberg

It began in layers with volunteers laying down thick sheets of cardboard to kill weeds, and then adding a mountain of horse manure and mulch. Within a few short years, the compost became black gold. Jay explained that he wasn't growing the plants to sell, but instead to give away-- to the volunteers and local folks who needed fresh food. It was a great success, and urban permaculture gardens took hold in the City by the Bay. 

Hayes Valley Farm was decommissioned by the City of San Francisco a few years ago, but it provided the seeds for starting other permaculture gardens in other neighborhoods. Now known as 49 Farms, their goal is to have a public permaculture garden for every square mile of the city. And it works. Find out more about 49 Farms and their good work at their website at https://sites.google.com/site/49farms/home