Thursday, January 16, 2020

Dead Fern Mapping at Seward Park


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:

Friday, January 10, 2020

Latest Map - with detailed summer assays of 14 sites


Click on map to visit interactive version.



Detailed tabular assay data included for 14 sites:
click on site to see popup.
(January 10th, 2020)
Note two Oregon sites, east-west extent in lowlands from Olympic
to Snoqualmie National Forests

Monday, December 9, 2019

KUOW's brief report and subsequent retraction

Last Thursday, December 5th, I heard from a couple of friends that KUOW had a 20-second afternoon (maybe drive-time) news spot reporting that the ferns at Seward were recovering.

Alas, not so.

It is easy to understand KUOW's misinterpretation of the  South Seattle Emerald article.   KUOW followed up with a correction the next day.

The on-air retraction, just like the original report, was only 20 seconds long.   Here's what they might have aired if they had more time:

Now, a clarification on a story we ran Thursday about sword ferns dying in Seward Park.  At Seward, at other sites in the Puget lowlands - from the Kitsap Peninsula to the Snoqualmie National Forest, and now also in a few sites just reported from Oregon -  sword ferns are experiencing an unprecedented and mysterious die-off, with no recovery in sight.  

Sword ferns are common, hardy and long-lived.  Just like their larger ecosystem companion, the Douglas Fir, they colonize open ground, then live for centuries without reproducing.  This unusual life cycle means that, once lost to an intact forest, they do not return.  Nor do other native plants - at least not quickly.  This loss of understory and ground cover creates a serious "ecosystem hole”.  This is a situation unlike what PNW forests normally experience, where an ecosystem disturbance also takes out the forest canopy, the overstory, and ample sunlight hits the ground to drive new growth. At Seward, the normal recovery of a disturbed forest - after fire, flood, insects, windstorms - is simply not happening.

In response to this, volunteers and Seattle Parks are engaged in labor-intensive restoration at Seward Park, filling in where the ground has been bare for five years.  They have planted nursery-grown native plants - including ferns - and hand-watering them through the summer drought. The natural regeneration we mentioned in our reporting on Thursday story is very limited:  after five years,  only ten small, seasonal plants of just one species (the Fragrant Fringecup) has sprung up in the acres of forest which used to be filled with sword ferns.

The cause of the die-off is still a mystery - but recent lab work strongly suggests that a pathogen is involved. Citizens, students and a few university scientists are working together, without pay, on this ongoing problem.  They track the die-off throughout the region, run experiments to figure out the cause, and hope eventually to find an effective response. 

Here's the actual story as it aired on Thursday 12/5  (my emphasis):

Some good news from Seattle's Seward Park.

In 2017, sword ferns there were mysteriously dying ... about a third of them were lost.  But the South Seattle Emerald reports that re-planting has been successful ... and there are signs of natural regeneration.  The Emerald says a women's group raised thousands of dollars to study the die-off.  And early research suggests that it's not drought that was responsible ... but some kind of pathogen.



Monday, December 2, 2019

Recent Findings and Community Support

We received a very generous donation last summer.   Laboratory & greenhouse research, and extensive regional die-off site surveys provide new insight into the nature and extent of the ongoing sword fern die-off.   Herewith an update.


  • The Seattle branch of 100 Women Who Care raised almost $8000 to support research into the cause and nature of the sword fern die-off.  We were delighted.  We are grateful!
  • Forest ecologist Dylan Mendenhall (trained at UW and UBC, himself once a Seattle Parks GSP forest steward at Schmitz Preserve) has conducted pro bono research at the UW CUH greenhouse over the last two months.    Greenhouse rental fees and material costs were paid for out of the 100 WWC donation.   Dylan tested the hypothesis first raised in the ad hoc beer-bottle experiment: that the die-off effect can be transmitted in water from an affected frond to a healthy frond.   Dylan's experiments proved this hypothesis, at scale, and with rigor - a huge breakthrough in our ongoing effort to determine the cause of the regional PNW lowland sword-fern die-off.  High resolution microscopy and metagenomic sequencing are likely next steps.
  • Reed College undergraduate researcher Caleb Goldstein-Miller, working under the guidance of Professor Aaron Ramirez, spent many weeks over the summer, and some subsequent time in the lab, on two topics: a regional die-off site survey, and ecophysiological water relations.   The results of the regional survey may be seen in this map.  (UW students and Dr. Tim Billo assisted in the survey.)  Caleb summarized the ecophys lab work: "[W]e are confident in our conclusion that moisture stress is not driving the die off at Seward Park. This increases our confidence that the regional decline is caused by some still unknown biotic vector".
  • Seattle Parks ecologist Lisa Cieko led (and continues to guide) a crucial response to the die-off at Seward Park: the ecological restoration of the original die-off site, "Ground Zero".  About 100 native plants of mixed species were installed, mulched, then watered over the summer, with thus far good survival rates.  In combination with the 24 sword ferns we planted in February of 2018 - which have a nearly 100% survival rate - Ground Zero is no longer the barren, non-regenerating  slope it was for several years.  In addition, a few fringecups have sprung up in the first instance of natural regeneration. 

Sunday, September 8, 2019

Visit to NatureBridge School in Olympic National Park

With an invitation from education manager Chris Morgan, I paid a visit and gave a talk to the educational staff at NatureBridge, on the shore of Lake Crescent.   I had an engaging exchange with about twenty staff members, all of them environmental educators whose mission

"is to connect young people to the wonder and science of the natural world, igniting self-discovery and inspiring stewardship of our planet. Through our overnight, hands-on environmental science programs, we take more than 35,000 children and teens each year into our national parks to explore the outdoors, connect with their peers, discover themselves and develop a lasting relationship with the environment." 

The low elevation mature and old-growth forests surrounding Lake Crescent are healthy.  Sword ferns dominate large areas of undergrowth - with no sign of any die-off.

We emerged from this meeting, which concluded with a walk in the woods, with a tentative plan: that NatureBridge staff and their students may contribute to understanding the die-off, and more fundamentally to the understanding the ecology and biology of sword ferns, through careful  observations over the coming years. 

Some of the topics we discussed:

  1.  Sword ferns rarely reproduce under a closed forest canopy.  See Robbin Moran's  Natural History of Ferns report that the prothallus (the gametophyte) needs recently exposed bare soil (and presumably ample sunlight) for propagation.  
  2. Individual plants (the familiar sporophyte generation) are very long-lived ("a thousand years is not out of the question" - David Barrington, University of Vermont polystichum expert)
  3.  Are there any signs of fern mortality, or propagation, in the healthy fern communities in Olympic National Park?  To suppport or contradict topics 1 and 2?
 We know little about the variability of the annual life cycle of healthy ferns and their fronds.   Perhaps a multi-year phenology project would be a good match for NatureBridge students?   A combination of careful observation in the forest, data collection, hypothesis generation and testing?

In this scenario, student scientists, backed up by trained academics (we have contacts with some helpful ones) could contribute new understanding of this signature PNW species, and provide baseline and background information we need to explore the die-off

Is there a pattern to the 10% sword fern survival at Ground Zero?


In 2013, 215 large healthy sword ferns occupied the understory of the quarter-acre of Seward Park's Ground Zero.  Twenty of those ferns survive six years later. Is there a pattern to that survival, perhaps some clue to the cause of the die-off?  It appears that proximity to trees or logs correlates with survival - but does that stand up to close inspection?  We found that there is a small but statistically significant association.

In this map dead ferns are black circles, survivors are in light green, trees are larger solid circles, and logs are thick black lines.

Leo Shannon and I collected the location and status of all ferns, trees and logs in this quarter acre on May 18th and 19th, 2019.   Dylan Mendenhall did the analysis.   Results are summarized below the map.



Dylan's summary and suggestions:

The survival rate was 10.2% for sword ferns within 15 ft of a tree or log. In contrast, the survival rate was 2.3% for sword ferns further than 15 ft from a tree or log... the odds of a fern surviving are 4.8 times greater if it is located within 15 ft of a tree or log. 

Based on these findings, management recommendations are to:
  • Maintain or increase coarse woody debris and mature trees in natural areas
    susceptible to sword fern die-offs
  • Prioritize restoration planting within 10 ft of CWD or mature trees

All preliminary data, subsequent revisions, R scripts and figures are available on github