The process of determining if a weed is of concern starts with the Federal Weed Risk Assessment: “a science-based evaluation of the potential of a plant species to establish, spread, and cause harm in the United States”. Specific guidelines are established for conducting a weed risk assessment. The procedures for the assessment, and completed weed risk assessments are made available online through the USDA APHIS website.

Since the U.S. has many different climates, not all federal noxious weeds are able to grow in all regions of the U.S.. To determine which species are able to grow in Alaska, the Alaska Center For Conservation Science performs climate screening. The climate screening determines the relative similarity of climate in areas a weed is known to grow with three ecogeographic regions of Alaska. These ecogeographic regions include Pacific Maritime, Interior Boreal, and Arctic-Alpine (Figure 1). If the species is already present in one of those ecogeographic regions of Alaska, it is presumed suitable. If the species is not present, than suitability is determined by comparing similarity to of climatic conditions of areas the species is present worldwide with the climatic conditions of representative areas of the three ecogeographic regions using the CLIMEX climate matching program (CLIMEX 1999). The climate similarity must be at least 40% to identify the species as having potential to occur in the ecogeographic region.

State of Alaska map with North and West coastal areas, interior, and coastal South and East delineated

Figure 1 Ecogeographic Regions of Alaska

Black represents the Pacific Maritime, white represents the Interior-Boreal, and hatched represents the Arctic-Alpine ecogeographic regions of Alaska. The dashed grey line represents the Alaska-Canada border. Image from the UAA Center for Conservation Science.