I have mapped dead sword ferns on three successive Sunday afternoons. I include and collect lat/long for unambiguously dead ferns, in which all (or almost all) fronds are brown. Usually all that remains is a brown stubbly crown. The die-off is much broader than the map suggests. I will fill in the as-yet-unmapped regions in time.
On January 12th, I counted and geo-located dead ferns in the trail-encircled area shownabove. This area has the healthiest population of sword ferns remaining in Seward's forest. Despite the dominance of healthy ferns, the die-off has reached into this area as well.
One surprise emerge. Last summer David Perasso established that even an apparently dead fern can sprout small fronds in the spring, apparently supported by a small amount of remnant healthy tissue in the rhizome. In the area I surveyed today, I found about a dozen classically dead crowns which had nonetheless a few full-size fronds coming out of them. This may be due to the cooler, wetter summer of 2019, which perhaps allowed these resprouted-from-remnant-rhizome fronds to live and grow through the summer. More observation may help to clear that up.
In the marked survey area above, I estimate that dead ferns are less than 3% of the total fern population.
Sunday, January 19th 2020: 251 additional dead fern geo-locations, from the northwest corner of the forest:
