Connecting Ag to Climate: Rangeland Productivity

In the wake of heat advisories and lower chances of precipitation across the region, grassland conditions in Wyoming have likely reached their peak, especially in pastures with cool-season grasses. 

The Grass-Cast forecast estimates how many pounds per acre are expected to grow on rangelands at the peak of the growing season, compared to the long-term average. The three adjacent maps show forecasted production if precipitation from July 9 through August 31 is above normal (left map), near normal (middle) or below normal (right). 

Notice the Grass-Cast maps, made July 9, look similar across the three precipitation probabilities. This is because the timing for the most important rainfall on rangelands has already passed in our region. Unfortunately, many of these rangelands did not get adequate moisture.

Looking ahead to the rest of the growing season, the odds are tilted towards below normal precipitation for Wyoming, according to the National Oceanic and Atmospheric Administration’s (NOAA) seasonal precipitation outlook.

The Grass-Cast map on the right shows more orange and even some red spots across Eastern Wyoming. This means if this area receives below normal precipitation between July 9 and August 31, areas in orange should expect a 15 to 30 percent reduction in grassland production. 

In red areas, like Southeastern Wyoming, producers should expect a 30 percent or worse reduction in pounds per acre compared to the area’s long-term average. 

Interested individuals can find more specific production estimates for their local area by visiting the zoomable maps at grasscast.unl.edu. 

Remember, Grass-Cast provides estimates of total production, not grazeable production. When using the “take-half, leave-half” rule of thumb, a 30 percent reduction in total production could equate to something closer to a 60 percent reduction in grazeable production.   

Averi Reynolds is an ORISE science communications fellow for the USDA Northern Plains Climate Hub, serving Wyoming, Montana, Colorado, Nebraska, South Dakota and North Dakota. The USDA Northern Plains Climate Hub strives to provide unbiased information about adaptation and mitigation strategies for ranchers, farmers and foresters to help increase their operations’ resilience to weather variability and a changing climate. For more information on the Northern Plains Climate Hub, visit climatehubs.usda.gov/hubs/northern-plains.