Applied Ecosystem Services, LLC

The Environmental Issues Doctor

Photo of Explaining Environmental Data


Estimated reading time: 1 minutes

Most people are familiar with statistical hypothesis tests such as the t-test and ANOVA to analyze whether two or more samples (from a parametric distribution) came from the same population. The nonparametric equivalents (Wilcoxon and Kruskal-Wallis tests) are less familiar but equally robust. What is not always clear is that these models are applied to one or more response variables; e.g., chemical concentrations that result from natural or anthropogenic causes. They do not answer the question of why these values were observed.

Regulators, stake holders, and environmental NGOs question the potential for adverse project effects on natural ecosystems, particularly surface waters, fish, and wildlife. These concerns are expressed at all stages of a project’s life cycle. One aspect of effectively addressing these concerns requires including explanatory and response variables in the statistical model to estimate how much response variability is explained by each explanatory variable. Which statistical model to apply depends on the specifics of the concern and the nature of the data (e.g., chemical or biological).

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 Environmental Issues Involving Fish and Wildlife

    Environmental Issues Involving Fish and Wildlife


    Estimated reading time: 2 minutes

    There are many plant and animal species considered to be threatened, endangered, or of special concern to regulators and the public. Correctly estimating population sizes, relationship to habitats, and potential effects of industrial activities is crucial to many permit issues and lawsuits. Other environmental issues are more broad, such as quantifying relationships of industrial activities and natural ecosystems. The most effective approach to addressing these issues is to quantify causality (cause-and-effect) and explain it in language understood by non-technical decision-makers or finders of fact.
  2. Photo of Factors Limiting Species Populations: 2

    Factors Limiting Species Populations: 2


    Estimated reading time: 2 minutes

    Habitat use is one of the first factors considered when determining limitations on species abundance and distribution. For species being considered for some level of protection there are existing data describing habitats in which they have been found as well as abundance estimates. When projects are proposed in areas with potential habitats for the species it is common to survey these habitats for the species’ presence. The survey methods seek data to answer this question: What is the probability of the species occupying a site if it is not observed during a visit?

Contact me when your data analyses must be technically sound and legally defensible.