Critical physical geography: State-and-transition models

I came across a solicitation to a dissertation workshop on “critical physical geography” which was a field I had never heard of before. Accompanying the solicitation was an introduction to a special issue of Progress in Physical Geography on the field, written by Rebecca Lave (link). I want to explore some of the intersections between what we think of as the mission of Borrowed Lands and critical physical geography.

Chris Van Dyke’s contribution to the special issue, “Boxing daze — using state-and-transition models to explore the evolution of socio-biophysical landscapes” (abstract) focuses on a type of model I spend a lot of time thinking about, what he calls the state-and-transition model. In the state-and-transition model framework, there are distinct landscape states, grassland and shrubland, say, and transitions which flip a landscape from one state to another such as grazing or fire.

State-and-transition model example
Figure 1 from Van Dyke (2015) illustrates a three-state STM




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Literary ha-has

When people modify landscapes, their interventions often reflect ideas about what to reveal and what to conceal. Beautiful vistas prompt the construction of scenic overlooks; drainage ditches cue the strategic planting of trees. It’s no secret that landscape architects structure environments in ways that achieve certain behavioral, social, and ecological effects. But people who write about landscapes do this, too. A description of a place is also an argument about how to experience that place. What has the author decided to say—or not say?

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Desire paths: visualizing haste and delay

I live near a shopping mall complex, and sometimes I feel like there’s not much to say about my local landscape. But the other day, I saw something that reminded me people don’t stop interacting with their environment just because it’s planned and suburban:

Desire path

Students of landscape architecture will recognize this eroded trail as a desire line, or desire path. These paths appear when pedestrians (or cyclists, cows, etc.) establish alternatives to constructed routes, usually in search of a shortcut—or a path where none exists.

Desire paths may exist in physical space, but they also represent flows of information. Some landscape planners interpret desire paths as evidence that an existing design has failed to meet human needs. Others celebrate crowd-sourced routes as the best way to begin designing cities and public transportation systems. Even in the digital world, our desire for efficiency drives us to scan webpages in distinct patterns. No wonder that desire paths are a touchstone for architects, web developers, and others interested in user-centered design.

In suburban and urban areas, however, certain pedestrians can create paths that halt movement and reflect more aesthetic—or self-absorbed—desires. Matthew Tiessen writes that the “Meanderthal” who frequently stops to text, take a photo, chat, or admire a scene is “a new species of urban flâneur … the proverbial stick in the spokes [that brings] the urban dweller’s expectations of mobility to an abrupt end.” Meanderthals trace individualized desire paths when they obstruct the flow of traffic, oblivious to the wants and needs of fellow pedestrians. They also pose a special design challenge: their paths aren’t always visible or consistent. The Meanderthal only halts routes when there are other people to halt.

How might urban designers anticipate and divert these Meanderthal paths? And should they? For me, Tiessen’s article also raises a broader set of questions: which desires do we physically inscribe on our landscapes, which ones do we keep hidden, and why?

What makes a grassland?


There was an article published in the most recent issue of Science that seemed like a good way to get the ball rolling here at Borrowed Lands.

William J. Bond. 2016. “Ancient grasslands at risk” Science, Vol. 351, No. 6269, pp. 120-122.

When you look at a grassland, often you’re looking at what used to be a forest. Knowing that deforestation is a massive contributor to biodiversity loss and carbon dioxide emissions, you might be tempted to plant trees on your grassland, restoring the environment to its previous state.

But what if that grassland was never a forest and is, in fact, an ancient grassland? That’s the question Bond asks in this article, and one which I’ve seen pop up a lot over the past year. In that case, you may not want to blindly reforest the grassland.


Depiction of the life cycle of an underground tree in a tropical grassland. From Bond, Science 2016

A similar debate exists in the salt marsh community. Recent results have suggested that North American marshes may owe their origin to changes in sediment supply driven by colonial-era deforestation and that salt marshes may have an inherently short life-cycle. Conserving marshes exactly as they are now or trying to install marshes as part of a revitalized urban landscape doesn’t reflect their natural dynamics.

However, we may not want to simply recreate the natural dynamics of salt marshes. Instead of framing the question in terms of restoring environments to their pristine, unaltered or natural condition — a frame which may lead us to reforest grasslands that don’t look as old as they are — we need to think about what exactly the various ecosystems provide both to humans and to the local and global environments. Unfortunately, as Bond notes, we don’t even have good maps of old-growth grasslands, much less a firm grasp of their carbon and nutrient budgets, biodiversity, social and ecological roles and environmental history. Similar uncertainties exist in salt marshes, for instance in their carbon budgets.

Even if we do get a handle on these uncertainties, we may yet decide that a tropical forest is worth more than an ancient grassland or that some extra marshes on groynes might do wonders for Boston Harbor. Conservation is far from straightforward.

On the Borrowed Lands reading list: Forgotten Grasslands of the South: Natural History and Conservation by R.F. Noss. I saw this book at the Harvard Bookstore the other day, and now Bond cites it, so I think I’ll have a look at it.