Applied Ecosystem Services, LLC

The Environmental Issues Doctor

Photo of Organisms and Their Habitats


Estimated reading time: 2 minutes

Understanding relationships between organisms and their habitats is important to operators and regulators, as well as being critical to managing species with low population levels. Pacific salmon in the Columbia River system and sage grouse and Lahontan cutthroat trout in the Great Basin are among many examples where understanding the factors limiting the presence or number of individuals in a defined area need to be quantified in a technically sound an legally defensible way.

Spatial distribution of plants and animals are not random or regular, but clumped. Populations almost always exhibit strong spatial autocorrelation; i.e., espatially close organisms or populations are more similar to each other than they are to more remote individuals or populations. This spatial autocorrelation greatly affects most organism-habit models. These models are either specific to a single location and do not apply to other locations, or they are so general they provide no useful insights to any specific location.

The statistical family of regression models quantify relationships of organism numbers, densities, or biomass to explanatory habitat variables and are the tools of choice to evaluate factors limiting populations. Such knowledge is valuable for making ESA-listing decisions, recovery plans, and delisting criteria. This knowledge is also valuable for operators, regulators, and litigators to determine whether the regulated activity has measurable adverse impacts on organisms of concern.

This work was originally published on the Applied Ecosystem Services, LLC web site at

It is offered under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International license. In short, you may copy and redistribute the material in any medium or format as long as you credit Dr. Richard Shepard as the author. You may not use the material for commercial purposes, and you may not distribute modified versions.

Keep reading

  1. Photo of Standards for Non-Potable Water Quality

    Standards for Non-Potable Water Quality


    Estimated reading time: 2 minutes

    Chemical standards are appropriate for human drinking water sources, but generally not for non-potable waters supporting fish and wildlife. This is because water chemistry is highly variable, measurements are isolated in time and space, and point measures are difficult to interpret as suitable for fish and wildlife. Biological-based standards of water quality are more appropriate because the presence of aquatic organisms reflect water quality integrated over time and space. Biological water quality measures have been of interest to environmental scientists and regulators for about 40 years.
  2. Photo of Reference Areas

    Reference Areas


    Estimated reading time: 2 minutes

    Natural ecosystems are complex and highly variable at multiple size scales. Because of the difficulties of accurately summarizing complexity and variability in an index number, regulators often require a reference area for comparison with a proposed or reclaimed project area. Agreement on a suitable reference area may be a requirement prior to permitting or bond-release decisions for mining and logging operations. It is common for selection of an acceptable reference area to take a long time.

Contact me to learn hos to avoid fish and wildlife issues in your operations.