One of the main causes behind biodiversity loss is the reduction and fragmentation of natural habitats. The conversion of natural areas into agricultural, urban or other human-modified landscapes often leaves wild species confined to small and isolated areas of habitat, which can only support small local populations. The problem with small, isolated populations is that they are highly vulnerable to extinction caused by chance events (such as an epidemic or a natural disaster in the area), or by genetic erosion (dramatic loss of genetic diversity that weakens species and takes away their ability to adapt to new conditions).
On top of that, we now have the added concern of climate change, which is altering environmental conditions and shifting habitats to different latitudes and altitudes. To survive in the face of these changes, many species need to modify their geographical distribution and reach new areas with suitable conditions. The combination of mobility (a biological property of species) and the possibility of spatial movement (a physical property of the landscape) is critically important for this. Continue reading →
In the UK, National Tree Week (26 November – 4 December) celebrates tree planting within local communities. The latest BES cross-journal Virtual Issue contains recent papers that highlight the global importance of trees and forests as habitat – for species from insects to primates – and in meeting human needs for fuel and agriculture. The selected papers also demonstrate novel methods scientists are using to study trees and forests.
National Tree Week is the UK’s largest tree celebration. It was started in 1975 by the Tree Council and has grown into an event that brings hundreds of organisations together to mark the beginning of Britain’s winter tree planting season.
Landscape connectivity is important for the ecology and genetics of populations threatened by climate change and habitat fragmentation. To begin our Virtual Issue Rayfield et al. present a method for identifying a multipurpose network of forest patches that promotes both short- and long-range connectivity. Their approach can be tailored to local, regional and continental conservation initiatives to protect essential species movements that will allow biodiversity to persist in a changing climate. The authors illustrate their method in the agroecosystem bordered by the Laurentian and Appalachian mountain ranges, that surrounds Montreal.
Scientists at the University of Liverpool have developed a new ‘route planner’ tool that could help conservationists aid the movement of species as they adapt to a changing climate.
The environmental ranges of many animal and plant species are starting to alter with climate change, as temperatures change and force species to migrate to more suitable climes.
To be able to do this successfully, they will need sufficient habitat in their existing range, their future range, and any intermediate areas to enable populations to survive and thrive. Many conservation initiatives to restore habitats and increase connectivity are trying to address this issue. However, existing modelling tools mainly treat the landscape as static, and it is difficult to use these to plan restoration. Continue reading →
Climate change and habitat fragmentation are interacting threats: it is likely that many species cannot reach newly suitable areas at the cool edge of their range because there is not enough habitat, in the right places, to support range expansion over multiple generations. Conservation efforts are already underway to restore large areas of habitat, and to improve the “connectivity” within networks of habitat. However, there are multiple ways of measuring connectivity and few of them address the scale of shifts that are likely to be needed under climate change. This could be a problem if it leads to inefficient conservation prioritisation.
The Conductance Metric
How conductance generally depends on the amount of habitat in the landscape. Squares show the conductance of landscapes with a random selection of cells chosen to be habitat. The red line is based only on the 100% point and the expectation that conductance is proportional to amount of habitat squared.
We first developed the conductance metric in 2012 and we found that it is correlated to the speed with which a species can spread through a landscape, from a specified source location to a specified target. A key difference between this and most other connectivity metrics is that it incorporates both reproduction within habitat patches and dispersal between habitat patches, over multiple generations (further explanation here). Sometimes there could be many very well-connected patches in a network, and yet no easy way for a species to cross the landscape from end to end. This could be a problem for the species’ survival, if staying within its current regions of occupancy is unsustainable, for example if it is being pushed northwards by climate change. Continue reading →