Landscape Ecology
Terms/people to know:
landscape ecology interdisciplinary
Turner 1989 Hobbs 1997 Wiens 1992
Carl Troll Izaak Zonneveld Richard Forman
Frank Golley John Wiens
Risser et al. (Allenton Park workshop)
European vs. North American versions of LE
Introduction: what is landscape ecology, really?
Space: The Final Frontier
Space is the final frontier in ecology (as in Star Trek). Most of ecology’s history has been played out in a nonspatial arena: predators perfectly mixed with prey, ecosystems were conceived as homogeneous pools of carbon or nutrients, and so on. This is not to say that there weren't a few people who worked on spatial problems, but they were definitely in the minority. And yet, space is inherent in ecology:
· Ecology is defined as the interaction of organisms and their environment, and their environment is profoundly spatial (because everything has to happen somewhere).
· Ecology is also defined in terms of interactions, and one thing that seems to be true of interactions in general is that their strength varies with distance: this is true of planetary gravitation, and it's true of competition for resources between individual plants. And distance implies spatial location.
The study of spatial patterns is the primary focus of a relatively young field called landscape ecology. "Landscape ecology explicitly addresses the importance of spatial configuration for ecological processes" (Turner and Gardner 2015).
But what is meant by “pattern,” anyway? Webster’s dictionary defines pattern as “a distinctive form,” implying an entity that has some regularity about it (cf. randomness).
Pattern is a manifestation of process, and process is the creator of pattern. Landscape ecology might be defined best by its focus on this pattern-process relationship: how to characterize it, where it comes from, why it matters, and how it changes through time:
· Characterizing pattern involves detecting it--and the scale at which it is expressed--and then summarizing it (statistically or otherwise quantitatively).
· The agents of pattern formation include the physical abiotic template, demographic responses to this template, and disturbance regimes overlaid on these.
· An interest in landscape dynamics often invokes temporal predictive models of some sort--because landscape are large and they usually change over timescales that are difficult to observe directly.
· Spatial heterogeneity matters to populations, communities, and ecosystems--and this has a profound impact on a variety of practical applications, including:
-design of conservation reserves
-land-use planning (e.g. urban development)
-watershed mgmt to protect water quality and aquatic resources
-forest mgmt (for both timber and non-timber)
-restoration of degraded lands
OK, so then what is a landscape?
Dictionary definitions:
- A picture representing a view of natural inland scenery (as of prairie, woodland, mountains, etc.)
- A portion of land or expanse of natural scenery as seen by the eye in a single view
Ecological definitions:
- Forman & Godron (1986): A heterogeneous land area composed of a cluster or interacting ecosystems that is repeated in similar form throughout (usually square kilometers in area).
- Naveh (1987): Landscapes include physical, ecological and geographical entities, integrating all natural and anthropogenic patterns and processes.
- Forman (1995): A kilometers‑wide mosaic over which local ecosystems recur.
A general definition of landscape may therefore be: A mosaic of patches and other structural elements that connect them in a given area; or simply a spatially heterogeneous area; or more simply an ecological mosaic! A landscape may or may not have a specific size, although humans usually associate a large size with it.
Here is a brief synopsis of the term:
Biblical times - use of “landscape” in the Book of Psalms (equated with “scenery”)
Early 1800s - first use of “landscape” as a scientific term, by A. von Humboldt (equated with “landform”)
1939 - “landscape ecology” coined (in German) by Carl Troll, with landscape as a physical entity
How landscape ecology has variously been defined:
- "the effect of pattern on process" (Turner 1989)
- "focuses on (1) the spatial relationships among landscape elements, or ecosystems, (2) the flows of energy, mineral nutrients, and species among the elements, and (3) the ecological dynamics of the landscape mosaic through time" (Forman 1983)
- "deals with the effects of the spatial configuration of mosaics on a wide variety of ecological phenomena" (Wiens et al. 1993)
- the interrelationship among "pattern, process, and design" (Joan Nassauer's keynote address, 9 July 2007, World Congress of Landscape Ecology)
Does landscape ecology pertain only to large spatial areas? Why/why not?
Key foci in landscape ecology:
In terms of spatial heterogeneity, landscape ecology deals with how to characterize it, where it comes from, how it changes through time, and why this matters:
o How to characterize it: To characterize pattern, we first have to find it‑‑and the scale at which it is expressed‑‑and summarize it (statistically or otherwise quantitatively).
o Where it comes from: What causes patterns to form on a landscape? These include factors like the physical abiotic template, demographic responses to this template, and disturbance regimes overlaid on these.
o How pattern changes through time: Because landscapes are large and they change over long time scales, experiments are not usually possible. Because these scales are prevalent in landscape ecology, modeling is also important ‑ maybe more so here than elsewhere in ecology.
o Why pattern matters: Spatial heterogeneity matters to individuals, populations, communities, and ecosystems‑‑and this is critical to applied fields like conservation biology, natural resource management, and land use planning.
Landscape ecology focuses on six major areas of inquiry:
-to identify and understand how various processes generate and maintain landscape pattern
-to quantify landscape pattern and determine the scale(s) at which spatial pattern emerges
-to explore the effect that spatial pattern has on biotic and abiotic processes
-to study the interactions and exchanges that occur across spatially heterogeneous landscapes
-to understand the role of human land-use activities on landscape structure and function
-to develop sound ecological principles for the management of landscape heterogeneity
Some general questions that are addressed within the scope of landscape ecology are:
What biotic and abiotic processes are responsible for the formation and dynamics of landscape patterns?
At what scale does spatial structure emerge on landscapes?
How does spatial pattern affect ecological processes, such as the movement of organisms (or the flow of water, materials or nutrients) across landscapes?
How does landscape structure affect the spread of disturbances, such as fire or disease or invasive species?
How can a landscape ecological perspective contribute to better resource or land management?
What can landscape ecology contribute to the conservation of biodiversity?
Click here for a PDF of a list of important topics in landscape ecology. (You'll need Adobe Reader from www.adobe.com to read the PDF file.)
What is landscape ecology, really? Some meta-analyses:
John Wiens (a key player in landscape ecology and former president of the International Association for Landscape Ecology) performed a meta-analysis of papers published in the journal Landscape Ecology over its first 5 years (Wiens 1992). His findings showed:
-Most studies are conducted at a large scale: therefore, landscapes are usually seen as being large entities;
-Most studies are descriptive or conceptual, indicative of a young discipline;
-Methodologically, it is logistically difficult to do experiments with landscapes (because of replication/size issues);
-There is a considerable investment in models, owing to the daunting logistics of field studies;
-As study objects, there is a preoccupation with vegetation pattern and land use pattern;
-In particular, landscape ecologists tend to recognize humans as being an important part of the system (as creators of certain spatial patterns).
Richard Hobbs (another past president of the International Association for Landscape Ecology) later (1997) summarized the second 5 years of the journal. His findings:
-A decrease in purely descriptive work (i.e., with no quantification) and much more statistical analysis of patterns (landscape ecology discovers spatial statistics), but still no experiments.
The implication is that LE is maturing as a discipline, although it still has a ways to go. In particular, Hobbs (1997) admonishes that landscape ecology has thus far offered precious little of practical utility. He calls for a renewed emphasis on applying the concepts and theory of landscape ecology to real-world applications.
Landscape ecology is not simply a synonym for spatial ecology, or for large-scale ecology, or for applied landscape planning. Instead, LE combines all of these. LE is an interdisciplinary field whose focus is the effects of pattern on process. To quote Risser et al. (1984), "Landscape ecology is not a distinct discipline or simply a branch of ecology, but rather is the synthetic intersection of many related disciplines that focus on the spatial-temporal pattern of the landscape."
Furthermore, just because all ecology must occur somewhere does not make all ecology landscape ecology!
Two important aspects of landscape ecology distinguish it from other subdisciplines within ecology:
- Landscape ecology often focuses upon spatial and temporal extents that are much larger than those traditionally studied in ecology.
- Landscape ecology explicitly addresses the importance of spatial configuration for ecological processes. Not only is landscape ecology concerned with how much there is of a particular component but also with how it is arranged.
What we will cover in this course:
We will cover both the theoretical and empirical foundations of LE. We will examine how we study landscapes, and how these studies impact other disciplines like conservation biology. The sequence we will follow is: 1) roots/history of LE, 2) how to define and detect patterns, 3) importance of scale, 4) techniques we use to analyze patterns, 5) responses to patterns by individuals, populations, and communities, and 6) applications of LE.
1) Roots and history of LE
2) Detecting and characterizing landscape patterns
-Defining what a "patch" is, and devising aggregate descriptions of collections of patches (their sizes, diversity, and such);
-Examining landscape fragmentation (and its converse, connectedness);
-How does pattern develop: there are three agents of pattern formation (physical template of environmental constraints -- soils, topography, climate; biotic processes -- establishment and growth, dispersal, and mortality; and disturbance regimes -- fires, floods, storms, and human land use (which we will contrast to natural disturbances);
-Landscape dynamics, or how landscape pattern changes through time.
3) Importance of scale
4) Techniques we use to analyze spatial pattern
5) Implications of landscape heterogeneity and pattern
-Individuals (habitat selection);
-Populations and metapopulations (including source-sink relations; habitat connectedness and population persistence);
-Communities, and questions about diversity.
6) Practical applications of the principles from landscape ecology
-conservation biology and natural resource management
-landscape architecture
-ameliorating effects from urbanization
History of landscape ecology
Landscape ecology as a discipline has two evolutionary lines, which might be caricatured as the "European School" (which is also represented in the United States and elsewhere), and the "American School" (which is also common in Australia, Canada, and elsewhere). Click here for a figure.
A brief timeline (see also Wu 2013):
1972 - 1st society for landscape ecology formed, in the Netherlands
1980s - emergence of LE in North America
1981 - 1st landscape ecology meeting, the Netherlands; 1st landscape ecology paper presented to the Ecological Society of America; BioScience article on the field by Forman and Godron
1982 - International Association for Landscape Ecology (IALE) was established at the 6th International Symposium on Landscape Ecological Research in Piestany, Czechoslovakia
1983 - The Allerton Park (Illinois) Workshop on Landscape Ecology, organized by Risser et al., with 25 participants, set LE research agenda for North America (Risser et al. 1984)
1984 - Landscape Ecology: Theory and Application (Naveh and Lieberman); 1st landscape ecology section at the annual meeting of the Ecological Society of America
1986 - Landscape Ecology (Forman and Godron); 1st North American meeting (Athens, GA, with 100 participants); US chapter of IALE established
1987 - the scientific journal Landscape Ecology established
The European school:
Some key European (or European-style) landscape ecologists:
Carl Troll:
Izaak Zonneveld:
Richard Forman (an American):
Many others!
Summary of the European tradition:
-origin in geography
-stimulated by the development of aerial photography
-emphasis on human-dominated (esp. ag) landscapes, cultural importance of landscapes
-integrated into current discipline of land-use planning
The American school:
Some key American landscape ecologists:
Frank Golley:
Oak Ridge Nat’l Lab ("Oak Ridge Gang"): personnel included:
-Robert V. O’Neill
-Robert H. Gardner
-Monica G. Turner
-also: Kim With, Bill Hargrove, Virginia Dale
John Wiens:
Many others!
Summary of the North American tradition:
-some researchers (e.g. Forman, Golley) use an essentially European style
-most other adopt a style that emphasizes quantitative methods (incl. spatial stats, GIS, remote sensing), ignores or de-emphasizes social and cultural roles of landscapes and human aesthetics
I will be taking a North American approach in this course.
This dichotomy oversimplifies reality because such geographic division conceals the diverse and continuously evolving perspectives within each region. Many ecologists in North America have recognized the importance of humans in shaping landscapes for several decades. Although humans and their activities have been treated only as one of many factors interacting with spatial heterogeneity, more integrative studies have been emerging rapidly in the past few decades with the surging interest in urban ecology and sustainability in North America. On the other hand, the perspective of spatial heterogeneity has increasingly been recognized by landscape ecologists in Europe and the rest of the world. The current development of landscape ecology around the world seems to suggest a transition from a stage of diversification to one of consolidation or unification of key ideas and approaches. Both the European and North American perspectives are essential to the development of landscape ecology as a truly interdisciplinary science.
There are, of course, many other well-regarded landscape ecologists around the world, including (in alphabetical order): Jack Ahern, Lenore Fahrig, Almo Farina, Eric Gustafson, Richard Hobbs, Louis Iverson, Jianguo (“Jack”) Liu, Bruce Milne, David Mladenoff, Joan Nassauer, Zev Naveh, Paul Opdam, Jianguo (“Jingle”) Wu, and many others.
Landscape ecology is a relatively young field, despite a long-standing human recognition of the importance of pattern on process. Its recent emergence can be attributed to 3 factors (Turner and Gardner 2015):