"Landscape corridors are among the most important conservation strategies in the face of global changes such as habitat fragmentation, habitat destruction, and climate change"..............."Corridors are habitats that are typically long relative to their width, and they connect fragmented patches of habitat".................."They can vary greatly in size, shape, and composition"............"The main goal of corridors is to facilitate movement of individuals, through both dispersal and migration, so that gene flow and diversity are maintained between local(animal and plant) populations".............."By linking populations throughout the landscape, there is a lower chance for extinction and greater support for species richness"..........."Corridors work by increasing connectivity between patches that are isolated by human habitat fragmentation, caused primarily by urbanization, agriculture, and forestry"............."Plants and animals can use corridors for both dispersal and migration, two key movement patterns for species persistence".............."The human-dominated habitats surrounding most natural areas(including National and State Parks and Preserves) present barriers that plants and animals are unable or highly reluctant to move through"................ "These inhospitable places may have higher abundances of predators, lower resource availability, or reduced shelter"............."When a corridor is present, however, it provides an unbroken path of suitable habitat that can provide safe passage for animals or plants without being hindered as they travel through agricultural or urban landscapes"............."This connectivity is key to population persistence, as it promotes gene flow between populations and supports higher species diversity"

http://conservationcorridor.org/2019/01/how-wide-should-a-corridor-be/

How wide should a(Wildlife) corridor be?

Conservation Corridor; January 19, 2019

It’s one of the most common – and simplest – questions when it comes to landscape connectivity: what is the best width for a corridor? When connecting large landscapes, is 10 or 20 meters a wide enough path for species to move? Larger animals need larger corridors, but exactly how much larger? And what about species with very high or very low mobility, like birds or plants?

So just how wide should a corridor be? According to Northern Arizona University ecologist Paul Beier, the answer is straightforward enough: a corridor should be 2 kilometers wide.

A lone Wolf using a wildlife corridor to seek out a mate
and create a pack of its own

In his most recent essay, Beier reviews the limited research into corridor width, and acknowledges that this is one of the most frequent questions he is asked. His recommendation of a 2 km width stems from the need to consider several issues.

First, some species need more than one generation to traverse the corridor to the next protected patch, and therefore need a corridor big enough to accommodate their home range. A 2 km wide corridor could accommodate the majority of possible terrestrial mammals likely to become “corridor dwellers”.

Mother Black Bear aMnd cubs using Wildlife corridor

Second, edge effects can negatively impact individuals that are forced to live or move near the boundaries of a corridor. A 2 km wide corridor could effectively create enough space to eliminate edge effects within a majority of its area.

Last, the widest possible corridor in general provides the opportunity to incorporate more human recreational use. This may not be the primary focus of the corridor, but is often a selling point when leveraging political and economic support. A corridor 2 km wide can also support not only the focal species, but species that were not originally considered when the corridor was designed and implemented as well.

The Wildlands Network seeking to link up North America's open space

Few other studies have explicitly addressed the question of how wide a corridor should be, and they mostly do it at a small scale. For example, one study intended to determine the minimum corridor width for streams concluded that there was no one standard width that could effectively maximize biodiversity conservation. Another study on voles concluded that the best corridor width was 1 m wide, but it only tested corridors up to 3 m wide. A study on dispersal behavior of frogs and salamanders provides a useful method for determining optimal corridor width, but without providing explicit values.

A detailed map of the hoped for Western Wildway Network corridor

For now the question of corridor width remains, with the most applicable answer coming from Beier’s 2 km rule of thumb. Land managers, stakeholders, conservation planners, and communities in general would benefit from more research, more discussion, and better consensus to the answer of this challenging question.

Resources

Beier P. 2018. A rule of thumb for widths of conservation corridors. Conservation Biology. DOI: 10.1111/cobi.13256.

Determining corridor width (January 2015)

Spackman SC and Hughes JW. 1995. Assessment of minimum stream corridor width for biological conservation: species richness and distribution along mid-order streams in Vermont, USA. Biological Conservation 71(3): 325-32.

Andreassen HP, Halle S and Ims RA. 1996. Optimal width of movement corridors for root voles: not too narrow and not too wide. Journal of Applied Ecology 33: 63-70.

January 15th, 2019

http://conservationcorridor.org/corridor-toolbox/