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Posts by samnicol

How should we measure the importance habitats for spatially structured populations?

https://upload.wikimedia.org/wikipedia/commons/0/0b/Northern_Pintails_(Male_%26_Female)_I_IMG_0911.jpg

Many species live in spatially structured populations. For example, migratory species such as these Northern Pintail ducks use discrete habitat patches during their migration. How can we tell which habitats are most important for management, and how do we measure importance? The answer depends what we want to achieve and the kind of data that we have available. Image: Wikipedia (Image credit: JM Garg)

Our new paper came out in Ecological Indicators yesterday. In the paper we review the literature on metrics for managing spatially structured populations (i.e. metapopulations, migratory species populations). We ask the question: “what is the best way to measure the contribution of a habitat to the total population?” It’s a complicated question, partly because different theoretical approaches all have their preferred metrics. In the paper, we take a quick tour of graph theory, metapopulation theory and matrix models/perturbation analysis, and try to link the metrics developed in these literatures into a usable framework. We argue that the best metric depends on the management objective and the data available, and provide a simple framework for metric selection using these ideas.

The work was completed in collaboration with scientists from the US, Austria and Canada as a product of the NIMBioS Working Group on Habitat for Migratory Species. You can see their press release here.

Abstract:

Mobile species with complex spatial dynamics can be difficult to manage because their population distributions vary across space and time, and because the consequences of managing particular habitats are uncertain when evaluated at the level of the entire population. Metrics to assess the importance of habitats and pathways connecting habitats in a network are necessary to guide a variety of management decisions. Given the many metrics developed for spatially structured models, it can be challenging to select the most appropriate one for a particular decision. To guide the management of spatially structured populations, we define three classes of metrics describing habitat and pathway quality based on their data requirements (graph-based, occupancy-based, and demographic-based metrics) and synopsize the ecological literature relating to these classes. Applying the first steps of a formal decision-making approach (problem framing, objectives, and management actions), we assess the utility of metrics for particular types of management decisions. Our framework can help managers with problem framing, choosing metrics of habitat and pathway quality, and to elucidate the data needs for a particular metric. Our goal is to help managers to narrow the range of suitable metrics for a management project, and aid in decision-making to make the best use of limited resources.

Citation:

Nicol S, Weiderholt, Diffendorfer J, Mattsson B, Thogmartin W, Semmens D, Lopez-Hoffman L, Norris DR (2016) . A management-oriented framework for selecting metrics used to assess habitat- and path-specific quality in spatially structured populations. Ecological Indicators 69: 792-802. DOI:10.1016/j.ecolind.2016.05.027

What makes a fish want to live in the desert?

Did you know that there are fish living in the Australian desert? Obviously, fish need water, and that’s usually scarce in the desert. However large parts of arid Australia sit over the Great Artesian Basin, which is an area where groundwater is under such pressure that if you dig a well, it’ll come to the surface all by itself… no pumping required! This is good news for fish, because weak points in the aquifer mean that water seeps to the surface and forms permanent springs in the desert. Because these springs are so isolated from other sources of fish, unique species have evolved that live only in spring complexes. One of the best looking of these fish is the red-finned blue eye, Scaturiginichthys vermeilipinnis, which lives only in springs on a single property in central western Queensland, Edgbaston Reserve. I was lucky enough to visit Edgbaston at Easter Read more

Optimizing wetland habitats for waterfowl in a changing climate

Not all ducks are the same. Some like shallow water for dabbling, others like the deep stuff for diving, and some like something in-between. So how do you manage a wetland wildlife refuge to maintain the best mix of all three options? And what happens if the climate changes the amount of water that you have to work with? Those are the questions that we answered in our latest paper that has just come out in Climatic Change: Optimal water depth management on river-fed National Wildlife Refuges in a changing climate. Read more

How good are we at detecting ecological change? It depends on where you look!

Nicol S., Roach J., Griffith B. (2013). Spatial heterogeneity in statistical power to detect changes in lake area in Alaskan National Wildlife Refuges. Landscape Ecology 28:507-517.

How well can we detect ecological change? It’s a good question— in the media we often hear about how the climate is changing, but how do we measure change, and does the amount of change that you detect depend on where and how long you look for it? It turns out that measuring change is pretty hard, and that it’s possible to get wildly different answers to the question “is the environment changing?” Read more

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