This month's topic is Invasive Species

This newsletter is called Mesa Conservation Resource Connection, as it connects us to you! Natural resources encompass a variety of topics, including agriculture, animals, wind, water, plants, sunlight, and soil. Our goal is to connect you with knowledge, resources, and fresh ideas as we explore the vast topics of natural resources together.

What is an invasive species?

A species is classified as “invasive” if it is not native to an area and, if introduced, is likely to cause harm to human health, the environment, or the economy. Species can become invasive in an area because they often lack natural predators, can change the environment in ways that support their own growth and spread, allowing them to outcompete the native species.

Why are invasive species bad?

Invasive species are a growing issue across Colorado and are recognized as one of the leading threats to biodiversity. In addition to the environmental impact, these species can be a significant financial burden. A 2021 study estimated that invasive species have cost North America over $26 billion per year since 2010. These species can cause significant damage to agriculture, hydroelectric infrastructure, fisheries, forestry, and even human health.

Invasive species exist in many forms. While most people think of invasive plants and animals, viruses and fungi can also become invasive. One example is the chestnut blight, which began around 1912 and was caused by an invasive fungal pathogen introduced through infested Japanese chestnut nursery stock imported from Asia. Because the American chestnut had never been exposed to this pathogen, it had no resistance, and 99% of chestnut trees in North America were destroyed. Today, significant efforts are underway to develop a blight-resistant American chestnut, with promising results. This example demonstrates the major economic impact invasive species can have on forestry and agriculture.

A recent invasive species on Colorado’s Western Slope, the zebra mussel, was first detected in Highline Lake in 2022. Since then, five more lakes and the Colorado River from its confluence with the Eagle River to the Colorado–Utah border have become infested. Originally from Eastern Europe, zebra mussels have few predators in the U.S. and reproduce rapidly, outcompeting native species. They can clog water infrastructure, deplete phytoplankton (a key food for larval fish), which contributes to harmful algal blooms. Practicing Clean, Drain, and Dry by thoroughly cleaning equipment, draining all water, and allowing boats and gear to dry before entering another waterbody is essential to prevent the spread of zebra mussels in Colorado.

Invasive/Noxious Weeds

Invasive weeds, also known as noxious weeds, are a significant category of invasive species. These plants are highly aggressive and spread rapidly, posing serious threats to agricultural lands, public lands, and other areas. They can quickly grow out of control, intensify wildfires, reduce crop yields, increase soil erosion, and outcompete native plant species.

The Colorado Department of Agriculture classifies noxious weeds into three categories, List A, List B, and List C, each based on their distribution within the state and the level of control required. List A species are rare or not yet widely established and must be eradicated wherever they are found. List B species are more common but have small populations that require active management to prevent further spread. List C species are widespread, and control efforts focus on long-term management and containment.

The overall goal of this classification system is to prevent the introduction of new invasive weeds, eradicate small or emerging populations, and contain species that are already widespread. Through coordinated prevention, early detection, and control efforts, the harmful impacts of noxious weeds can be effectively minimized and managed.