Based on an August 2020 extract of the California Plant Rescue Database, California Botanic Garden has collected 2 seed accessions of Acmispon prostratus from 2 plant occurrences listed in the California Natural Diversity Database. These collections together emcompass 50 maternal plants

Based on an August 2020 extract of the California Plant Rescue Database, San Diego Zoo Global has collected 4 seed accessions of Acmispon prostratus from 4 plant occurrences listed in the California Natural Diversity Database. These collections together emcompass 250 maternal plants

Population or occurrence counts have varied in the past 20 years. It is believed there are roughly 40 historic locations in the US (all in San Diego County), with the number of extant occurrences hovering around 30. There are 21 occurrences on conserved lands. Many populations have declined as a result of invasive non-natives. Because it is an annual, some years populations seem to be doing very well, and other years there might be no individuals in a population. Furthermore, it is difficult to track whether a decline in numbers is a result of a weed invasion, trampling, or simply rain and temperature conditions. As with all annuals, it is difficult to count individuals persisting in the soil seed bank, but eradication of invasives in some locations might lead to the augmentation of existing populations, or the reestablishment of extirpated populations.

Human activity has led directly to the massive decline of this species. Acmispon prostratus has evolved to live in coastal sand dunes, many of which have been developed in the past for homes or cleared for recreational beaches or parks. The species is now restricted to a few beach locations and ocean lagoons and bays. Development is not the major threat to remaining populations as these lands are under restrictions and any development projects would likely require major mitigation projects. Invasive plants and trampling by people and dogs remain the largest threat to the species. Sahara mustard (Brassica tournefortii) has been particularly harmful to some populations. Many invasive grasses do very well in sandy substrates, invasive Limonium species, Carpobrotus, etc. are all very harmful. Some populations are protected by federally listed California least tern nesting areas, which are fully fenced and well managed.

Invasive species removal is the most needed management action for this species. The species is a good candidate for seed bulking and reintroduction into suitable areas once weeds are under control. Furthermore, extant populations could be augmented with seed that has been bulked ex-situ.

Research into the natural soil seed bank of this species could help predict the likelihood of rediscovering extirpated populations.

In 2016 San Diego Zoo Global made two seed collections from different populations on City of San Diego land. Germination trials of the seed showed that the collections were viable. Seed readily germinated, though it was not grown to maturity. I believe the species can be grown ex-situ, with subsequent seed collected and available for reintroduction or population augmentation.

Lotus nuttallianus is known from San Diego County, California and Baja California, Mexico. It is declining precipitously and is known from fewer than 26 extant occurrences in California. Land management activities, development and non-native plants are the major threats to this species.

Current threats to this species include development, invasive plant species, trampling, dogs, and land management activities (particularly by the United States Navy at Silver Strand and Imperial Beach) (NatureServe).

As of 2005, there are fewer than 26 extant occurrences in California (NatureServe).