The most frequently cited definition of the ecosystem
concept owes its origin to Sir Arthur G. Tansley in 1935 (Pickett and Grove 2009).
It has proven to be a very flexible concept, and can be applied to any
scale that includes aggregations of physical environment and organisms, plus
the interactions among all physical and biological components. The interactions are just as important as the
material, energy, and organisms that exist within ecosystems. Nevertheless, ecosystems are usually
specified as locations or places, that is volumes of some part of the Earth,
whether watery, dry land, or wetland (Figure 1).
 |
| Figure 1. Experimental watersheds at the Hubbard Brook Ecosystem Study in New Hampshire as ecosystems. Using the ecosystems as place perspective, the watersheds, with boundaries set by the flow of surface water into the receiving stream, are recognizable ecosystems for the purposes of research and modeling. A photograph of a landscape may represent one or many ecosystems, but it is necessary for the researchers or managers to specify the boundary of each system that the photo might show. |
Ecosystem as Interaction
Yet, there is a view of ecosystems that places the
interactions themselves as the focus.
This usage is most often heard in the vernacular or in discussions about
corporate products and the services they deliver. Hence, one hears about such things as the
"Apple ecosystem," or the "Google ecosystem," or the
"health care ecosystem."
Clearly such usages place the connections and flows of information,
products, or outcomes at the center of concern.
A bounded and contiguous place is not the point in this use of ecosystem
as a network.
Networks are a primary concern of many sciences. Information sciences, neurosciences,
industrial ecology, and studies of governance (Figure 2) often emphasize
connections and flows of information, power, influence, materials, and
energy. Traffic engineers and planners
envision their topic in terms of networks, although those networks can be seen
to serve both close and distant territories.
The network rather than the territory or place is the point.
 |
| Figure 2. A network approach to a system. This is a governance network, showing the connections between government agencies, non-governmental organizations, and community associations concerned with environmental stewardship. The connections represent the sharing of finances, resources, staff, or information. (From Romolini and Grove, 2013.) |
So it may seem that the network perspective and the place-delimited
view of ecosystem are contradictory and divergent approaches to science. But this is not the case. In fact, ecology is a science of interaction. A traditional definition of ecology states
that it is the study of the interaction between organisms and their
environments. However, this definition
can be expanded to acknowledge the variety of units or entities other than just
organisms that are involved in those interactions. For example, in the 1950s ecology expanded to
consider ecosystems as entities in which biogeochemical processes were the
concern. In the 1980s in the United
States, landscape ecology was imported and adapted to emphasize the
interactions that involved spatially heterogeneous mosaics at various scales. Even populations and communities came to be
seen as comprising subsets that interacted across space, as in metapopulation
or metacommunity theory. The explicitly
interaction-focused definitions of ecology (Box 1) work equally well with the
place-based or the network-based approachs to systems.
Box 1: The Cary Institute Definition of Ecology. The scientific study of the processes influencing the distribution and abundance of organisms, the interactions among organisms, and the interactions between organisms and the transformation and flux of energy and matter.
A network is also a system, but specifically a system of
interaction pathways, mechanisms, or flows.
In other words, a network can be considered to be an infrastructure or a
process that takes place over that infrastructure. Networks as infrastructure may involve
materially connected continuous pathways, like roads or wires. But infrastructural networks can also involve
fields, like broadcast via electromagnetic radiation (McGrath
and Shane 2012). Certainly, the
underlying fields are continuous, but the function of networks that rely on electromagnetic
media seem more discontinuous, since the information can travel great distances
with no tangible expression of the network until the message is delivered and
decoded.
Joining Networks and Places
Some theories in urban ecology attempt to deal simultaneously
with the place-based and network-based conceptions of systems. For example, the continuum of urbanity
recognizes that local to global connections are key to understanding urban
systems now (Seto et al. 2012, Boone et al. 2014). The fine scale connections can be via road,
rail, pipes, fiber, or copper. Even at
regional scales, these physical networks remain important. Shipping lanes and airline routes are a
different kind of infrastructure, but they support regional to global
connections in which urban areas partake.
Satellite communications, radio, and wireless act at various scales and
can be seen as virtual networks. The
regional and global networks have become a part of daily urban system
functioning.
These networks connect
places, and those places embody lifestyles, livelihoods, and environmental
conditions that are key drivers of urban ecosystem structure, function, and
change. The continuum of urbanity
expresses the seminal role of connections when it acknowledges that rural,
urban, and wild places -- ecosystems in the sense of Tansley -- contain and are
parts of extensive continuous and virtual networks. So ecosystems are both place and network.
Literature Cited
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Seto, and M. Yokohari. 2014. Reconceptualizing land for sustainable urbanity.
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McGrath, B., and G. Shane. 2012.
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Steward Pickett
