Defend the Core: Maintaining intact rangelands by reducing vulnerability to invasive annual grasses

 A new management strategy called “Defend the Core” is helping address the threat of invasive annual grasses at the scale needed to maintain healthy rangelands.

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“Defend the Core” presents a new paradigm for tackling rangeland threats

A proactive path forward to protect healthy sagebrush rangelands from invasive annual grasses

From the Great Plains to the Great Basin, an onslaught of invasive plants, including unwanted grasses like cheatgrass or woody species like eastern redcedar, are degrading rangeland health and agricultural productivity. A new paradigm in rangeland conservation and management is emerging to tackle this threat. Succinctly captured in the phrase “Defend the Core,” this approach leverages spatial data to focus rangeland management on proactive and preventative efforts that address large-scale threats within otherwise intact landscapes, or “cores.”

An upcoming paper in the journal Rangelands, supported by Working Lands for Wildlife (WLFW), and authored by Jeremy Maestas (NRCS West Technology Support Center), with support from Mark Porter (Oregon Department of Natural Agriculture), Dirac Twidwell (University of Nebraska), and Matt Cahill (The Nature Conservancy), further defines what the “Defend the Core” concept means for addressing the threat of invasive annual grasses in sagebrush country.

By applying a common vulnerability-based model to threat reduction, the authors describe how land managers can reduce the risk of annual grass invasion by implementing guiding actions at the scales needed to perpetuate healthy and resilient sagebrush rangelands.

Satellite-based technology is key to providing critical landscape context missing from past local management, allowing rangeland managers to visualize rangeland vegetation cover at a variety of scales, from pastures to entire biomes. This allows managers to identify large and intact rangeland cores where invasion is minimal and proactive and preventative measures can still be taken to reduce risks.

Understanding this landscape context allows managers to focus the right actions in the right place at the right time. For example, eliminating small infestations within a large, intact core landscape can help managers more effectively and efficiently prevent those infestations from expanding into the surrounding landscape. Conversely, attempting to save isolated islands of uninvaded lands in a landscape dominated by annual grasses is unlikely to have long-term success and requires different crisis mitigation strategies.

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Once cores are identified, successfully defending cores relies on understanding how vulnerable the land is to annual grasses and taking appropriate steps to address each component. The authors provide three guiding actions to assess vulnerability:

1) Reduce exposure to invasive seed sources. Without seed sources, annual grasses cannot invade rangeland cores. Exposure to seeds is the primary point of vulnerability that leads to annual grass conversion. Eliminating seed sources is the most effective way to reduce this risk.

2) Improve resilience and resistance by promoting perennial plants. The sensitivity of sagebrush rangelands to invasive annual grasses is well understood. This information can be leveraged to further reduce vulnerability. For instance, warmer and drier sites are more susceptible to invasion than cooler moister sites, but perennial grasses play a critical role in minimizing invasion as well. The authors argue long-term solutions lie in integrated approaches that manage for desired perennials and against invasive annuals.

3) Build capacity to adapt to changing conditions. Improving the ability of communities and partnerships to adapt to changing conditions and respond with appropriate actions in a timely manner is critical to minimizing impacts. This work includes enhancing the ability to learn and transfer knowledge quickly between land managers, scientists, and agencies, and providing flexible decision-making structures to empower local partners to be nimble and take action.

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Fortunately, roughly 70 percent of rangelands in the sagebrush biome still have relatively low amounts of annual grass cover, providing ample opportunity to implement the Defend the Core approach if we act today. Several statewide and regional efforts have already begun applying this approach to address invasive annuals across ownership boundaries, including:

• Idaho’s Cheatgrass Challenge
• Oregon’s SageCon Invasives Initiative
• Western Governors Association’s Toolkit for Invasive Annual Grass Management
• Western Association of Fish and Wildlife Agencies’ Sagebrush Conservation Strategy 

The Defend the Core approach also lies at the heart of NRCS Working Lands for Wildlife’s frameworks for conservation action in the grassland and sagebrush biomes, which seeks to address invasive annual grasses and other primary threats to native grasslands and shrublands of the western United States.

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Defend the core: Maintaining intact rangelands by reducing vulnerability to invasive annual grasses

Abstract: New geographic strategies provide the landscape context needed for effective management of invasive annual grasses in sagebrush country. Identifying and proactively defending intact rangeland cores from annual grass invasion is a top priority for management. Minimizing the vulnerability of rangeland cores to annual grass conversion includes reducing exposure to annual grass seed sources, reducing sensitivity by promoting perennials, and building the adaptive capacity of local communities to respond to the problem.

Citation: Jeremy D. Maestas, Mark Porter, Matt Cahill, Dirac Twidwell, Defend the core: Maintaining intact rangelands by reducing vulnerability to invasive annual grasses, Rangelands, 2022, ISSN 0190-0528.

Permanent URL: https://doi.org/10.1016/j.rala.2021.12.008

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