The Connectivity Analysis Toolkit is a software interface that provides conservation planners with advanced tools for linkage mapping and centrality analysis.

 

Why is connectivity important?

 

Conservation biologists have long recognized that natural areas that are linked into networks are often more effective than isolated areas at preserving certain components of biodiversity (Harris 1984, Noss and Harris 1986). Although in the past connectivity usually was considered in a static and purely structural sense as habitat corridors, we now recognize that planning for connectivity requires incorporating process as well as pattern into conservation planning, and that connectivity can be achieved by means other than corridors. There is increased awareness of the importance of ecological and demographic dynamics, including the dynamics resulting from human-associated landscape change, in determining the persistence of biodiversity.

 

Considering connectivity in landscape planning can facilitate:

 

1) Maintenance of demographic flows - The traditional focus of connectivity, e.g., rescue effect (Brown and Kodric-Brown 1977) of dispersal on populations inhabiting small patches.

2) Maintenance of genetic flows - Avoidance of inbreeding depression, long-term maintenance of genetic adaptability, diversification of evolutionary lineages, etc. through dispersal (Young and Clarke 2000)

3) Resilience of populations to landscape conversion by agriculture, forestry, and development, by evaluating the adequacy of reserve networks in the light of landscape-level threat processes.

4) Resilience of populations to climate change, by designing reserve networks that allow species to track suitable habitat (e.g., altitudinal migration) as it shifts in response to climate change

5) Maintenance of nutrient and hydraulic flows in freshwater systems

6) Maintenance of characteristic ecosystem processes necessary for population persistence - e.g., patch dynamics of disturbance or resources.

 

The focus of connectivity planning has increasingly shifted from preserving static elements of landscape structure such as corridors to facilitating these ecological processes. Structural connectivity is no longer seen as a distinct conservation goal, but rather as a means to maximize retention of functional connectivity, and thus achieve broader conservation goals such as species' persistence (Pressey et al. 2007).

 

How can connectivity be assessed during the landscape planning process?

 

A group of landscape metrics based on graph theory, termed centrality metrics, provides a means to quantitatively incorporate connectivity within the planning process by ranking the importance of sites as gatekeepers for flow across a landscape network. Computational advances now allow such metrics to be applied to landscapes of continuous habitat gradients represented as lattice-based graphs with large numbers of nodes. This approach avoids both the binary classification of landscapes into patch and matrix required by patch-based graph analyses, and the focus on single paths between individual pairs of source and target patches characteristic of most corridor mapping methods. The Connectivity Analysis Toolkit allows users to develop and compare three contrasting centrality metrics based on input data representing habitat suitability or permeability, in order to determine areas where conservation measures might facilitate connectivity and dispersal for a particular species.

 

The Connectivity Analysis Toolkit also allows application of these approaches to the more commonly considered problem of mapping habitat linkages between pairs of source and target patches. This represents a special case of centrality analysis, termed subset centrality, that also may benefit from comparison of results from the different metrics contained in the Toolkit.