If you haven’t heard the news, the monarch butterfly is under consideration for protection as a threatened species under the Section 4(d) of the Endangered Species Act. This journey began with a lawsuit from various environmental groups in 2014 and we are now reaching the finish line with this issue. FWS-R3-ES-2024-0137 is the docket number for the report. I spent the last few days reading this legal and scientific document and after drinking several liters of coffee, I am ready to opine and summarize it for you.

Deep breath . . .

What do I think are the immediate impacts on California strawberry growers?

Short answer: nothing until the proposal is examined by the Fish and Wildlife Service (hereafter referred to as Service) following public comment. This is a proposed ruling and nothing is set in stone yet. The proposal puts forth a recommendation that 4,395 acres from Marin County to Ventura County are to be designated as protected and critical habitat. The critical habitat is composed of a core, shelter, and support zone. All zones provide the physical and biological features essential to conservation. The support zone is the 500-foot protection buffer that goes around the core and shelter zone.

It is not clear if any strawberry growers are within these critically endangered areas when examining the index maps in the report (pp. 167-183). It remains to be seen if any strawberry growers will be affected by this proposed ruling. I have placed an example of such a map from the report below (Fig. 2). The whole report and its maps can be found here.

What reasons did the Service cite in the report?

Habitat loss is the main driving factor. It was estimated, for example, that 40% of the monarch population in the Midwest was lost from 1999-2014. The Service cites data that 4.9 million acres of grassland was converted to agricultural or urban development beginning in the 1990s. Herbicide use across agricultural systems in these converted areas led to the decline of milkweed which in turn decreased suitable breeding habitats for monarchs.

Climate change is claimed to be a threat because optimal maximum temperatures for monarch survival are between 81-84 °F. At 108 °F and above, the species is toast. They are also citing climate change as a threat to the survival of overwintering tree species. Monterey pines and Monterey cypress are drought resistant but are present in less than 25% of the overwintering sites. Eucalyptus, which constitutes a majority of the overwintering trees for western populations, has a tendency to easily catch fire. Extreme drought at overwintering sites poses catastrophic risk to the western population both directly to the monarch and indirectly by possibly killing the overwintering trees through fire and drought risk.

In addition, the overwintering tree for the eastern populations is the Oyamel fir in Mexico. This fir is expected to decline by 50% by 2050. Currently, the known overwintering sites in Mexico make up about 138,000 acres of land under threat of logging. Increasing temperatures and the loss of trees through illegal logging pose the greatest threat to the eastern monarch butterfly population.

There are also reports that as the climate warms, many monarchs decide to stay in their overwintering sites due to heat. This increases the risk of protozoan parasitism in these nonmigratory populations. This will undoubtedly cause some increased pressure to somehow save the nonmigratory populations. The report cites evidence that the nonmigratory populations currently do make up a significant percentage of the whole population of monarchs.

Insecticide use is also cited as a threat to monarchs based on mode of action. The report zeroes in on the liquid forms of lepidopteran (moth and butterfly) active Bacillus thuringiensis (Bt) products and if they are sprayable. The report cites direct spray or residual effects from consumption of contaminated leaves and nectar. Pyrethroids, neonicotinoids, and organophosphates are cited as potential threats but mostly in the context of regions “where mosquitoes pose a public health threat or reach nuisance levels.” Granular insecticides, herbicides, and fungicides are not considered a potential direct threat.

What is the current extinction risk?

The report states that the western population of monarchs is the most threatened with a 99% extinction possibility in the next 60 years. The western population faces the greatest risk of catastrophic events such as droughts and extreme storms which threaten the overwintering habitat. The population is smaller and spread out over a larger region than their siblings in the East. The Endangered Species Act only applies to the United States; therefore none of its recommendations would apply to Mexico.

What are next steps?

There is a 90-day comment period. The Service recommends comments backed by scientific reports or papers to add weight to them. Many agricultural organizations are currently discussing and digesting the report. Much of what is contained in the report is information that has been already published both in academic literature and government reports. The Service is requesting public comment on exceptions for pesticide use under the 4(d) rule. I would recommend adding your voice to conversation. I know I will be giving my two cents. The link to the public commenting for this docket can be found here.

In the meantime, if you want to learn more about monarch butterflies and farming, there is a great video from Western Growers about this topic posted below.