Shrub-steppe: Native & Invasive Weeds

The Hanford Reach National Monument’s ecosystem is named after the dominant plants. We call it shrub-steppe, which may sound like a dance, but it means “grassland with shrubs.” Deep root systems sustain many perennial types of grass and shrubs through the dry seasons, and also makes them able to regrow after a fire. But invaders have disrupted the usual cycle of fire and regrowth. 

The spaces between bunch grasses and shrubs, formerly covered with a living crust of mosses and lichens, are now occupied by cheatgrass. This annual grass, a weed brought from Eurasia as settlers moved across the continent, covers the ground like a thin carpet. This species “cheats” the soil of moisture and nutrients early in the spring, before the native grasses get started. Then as the weather heats up, it drops plenty of sharp-pointed seeds and dies. The resulting sea of brown stalks is more than just an annoyance, as those seeds get stuck in socks and animal fur and mouths. A lightning strike or hot car undercarriage can set off a hot-burning blaze that permanently damages shrubs like sagebrush. Tumbleweed, also called the Russian thistle, is another invasive weed that chokes out native plants and spreads the fire. We are seeing wildfires happen much more frequently with all these weeds in the landscape, and the native plants have a hard time keeping up. 

Exotic plants may thrive in a foreign ecosystem and even feed some of the animals and insects there, but without the species that evolved alongside it, there’s a risk of that plant growing and spreading unchecked. Natural predators or controls are just not there, and the plant becomes a nuisance. In contrast, native plants nourish the food web with their numerous connections to other living things. Plants are the essential first link in the food chain and both shelter and nursery for creatures of many sizes. In the shrub-steppe, native bunch grasses provide cover for ground-dwelling birds such as quail and grouse, something cheatgrass can’t do. Many butterflies and moth caterpillars eat a specialized diet, relying on only one or a few plant species for survival. A healthy ecosystem starts with a diversity of native plants. 


U.S. Fish & Wildlife Service manages the land and resources of the Hanford Reach National Monument. You can find more information about the threat that invasive weeds pose to the ecosystem in their weed guide here, and learn more about rare plant species, including some that are found nowhere else in the world, on their page about unique plants. 

Integrated Environmental and Sustainability Education Learning Standards 

Standard 1 Students develop knowledge of the interconnections and interdependency of ecological, social, and economic systems. They demonstrate understanding of how the health of these systems determines the sustainability of natural and human communities at local, regional, national, tribal, and global levels 


Next Generation Science Standards

K-LS 1-1: Use observations to describe patterns of what plants and animals (including humans) need to survive 

2-ESS 1-1: Use information from several sources to provide evidence that Earth events can occur quickly or slowly 

2-ETS 1-1: Ask questions, make observations, and gather information about a situation people want to change to define a simple problem that can be solved through the development of a new or improved object or tool 

3-LS 3-2: Use evidence to support the explanation that traits can be influenced by the environment 

4-LS 1-1: Construct an argument that plants and animals have internal and external structures that function to support survival, growth, behavior, and reproduction 

5-LS 1-1: Support an argument that plants get the materials they need for growth chiefly from air and water 


Washington State Social Studies Learning Standards

G2.K.2 Identify natural events or physical features such as air, water, land, or wind. 

G2.1.4 Identify natural events or physical features. 

G2.2.1 Identify some common and unique cultural and environmental characteristics of specific places. 

G2.3.1 Explain how the environment affects cultural groups and how groups affect the environment. 

SSS1.4.1 Identify the concepts used in documents and sources.  

SSS1.4.2 Evaluate primary and secondary sources. 

SSS2.4.2 Identify the main ideas from a variety of print and non-print texts.