Ocean Beach Off-Leash Closure
Hatch Report Analysis
The Closure
Hatch Report Analysis
Plover or Sanderling?
Take me Home



By Dr. Suzanne M. Valente  (Nov. 9, 2006)


This is the second report Daphne Hatch (Chief of Natural Resource Management and Science for the Golden Gate National Recreation Area) has produced for the GGNRA to justify the closure of most of Ocean Beach to off-leash recreation due to the transient presence of the Western Snowy Plover (WSP).  The first was produced in 1996 and can be found on the Ocean Beach DOG web site (Click here to see the 1996 Hatch Report). The second report, dated November 2, 2006, is the subject of this analysis. Reading Ms. Hatch’s report brings to mind an article I recently read from the Journal of the American Dental Association October 2006 Special Supplement.  The article was entitled, “Challenges in Interpreting Study Results—The conflict between appearance and reality”.  It seems that the GGNRA and Ms. Hatch have endeavored to manipulate the data so as to reach a predetermined outcome. Their conclusions falsely give the reader the appearance that the threat to the WSP from off-leash dogs is great. The reality is there is no credible threat to the WSP from off-leash dogs within the GGNRA. 


Bias: The 2006 Hatch report presents itself as an “observational study”.  Observational studies have the least reliability of any type of scientific study because their results can be distorted by many factors.  The first of those factors is bias.  Bias generally stated is a “systematic error in the design, conduct, or analysis of a study that results in a mistaken estimate of an exposure’s effect on the risk a subject faces”.  Bias is the basis of our skepticism of research to determine the efficacy of a medication when the research is conducted by a clinician who stands to gain financially if the medication is shown to be effective. 


Ms. Hatch clearly has an ideological bias against people and their dogs recreating in any manner at Ocean Beach.  She was quoted on September 7, 2005 in the S.F. Chronicle as saying, "Ocean Beach without the people is an incredible habitat. But people think of it as a sandbox or their backyard” (see OBDOG web site section “Quote of the Day”).  This is an incredible admission from a high ranking GGNRA official considering the enabling legislation of the GGNRA.


Design:  Daphne Hatch’s bias is apparent in the design of this study.  The objective of this study is to prove her assumption that the present management which allows off-leash dog use of Ocean Beach and Crissy Field is inadequate to protect the WSP from harassment/disturbance and other detrimental effects of chasing by dogs.  We learn nothing about the relative harassment/disturbance of the plover from any other source in this study.  If plovers are harassed/disturbed 50 times in 5.5 hours by ravens, and one time in that same time period by a dog, is the harassment/disturbance by the dog even relevant?  A comparative study model would have been more informative with respect to actually determining what management actions, if any, should be taken to protect the plover from harassment/disturbance in general.  Frankly, this comparative study should have been undertaken in 1993 when the WSP was first listed as a threatened species, before the decision was made (and later reversed by the Federal Court) to require the leashing of dogs to protect the plover.  However, it could have been undertaken at any time.  A comparative study is designed to remove one variable in a situation at a time, and observe the change, if any.  An initial period of observation would document the presence of predators (ravens) and their numbers, as well as the frequency of harassment/disturbance from all sources absent any management action.  Next, the predators (ravens) being the most serious source of potential disturbance/harassment are removed as much as possible.  Rather than killing all the ravens, the GGNRA could have begun a campaign to reduce and remove litter at the beach as a conservative method to reduce the number of ravens. This would entail aggressive ticketing of those who are observed leaving litter at the beach, and resources would be deployed to clear the beach of litter and dead wildlife daily.  No one would be adversely affected, and in fact most beachgoers would welcome a cleaner, safer beach.  Indirectly, the lack of litter/foodstuff for the ravens would have been expected to reduce their numbers.  After the new management practice has been implemented for a reasonable period of time, a second period of observation is conducted.  In this second data collection period, we could assess whether the litter reduction has reduced the number of ravens, and has the reduction in ravens reduced the frequency of harassment/disturbance to the WSP.  If the ravens are not reduced, or the frequency of harassment/disturbance is still unacceptable, the next management measure is implemented.  Exclosure fencing could have been placed in the areas where the WSP is observed roosting.  This would serve to provide some protection for the WSP from the ravens and any other predators, as well as humans and dogs.  Education of the public to give the exclosure fencing a wide berth would be appropriate.  After a reasonable period of implementation, a third period of observation would be conducted to determine what effect, if any, this latest management method had upon the frequency of harassment/disturbance of the WSP.  There also should be the implementation of an aggressive ticketing policy for all dog owners whose dogs were observed chasing plovers at some point within this process.  All of these management measures should have been implemented and assessed for their effectiveness in reducing the frequency of WSP harassment/disturbances before a leash restriction was even considered.  This would have been consistent with the mandate to maintain recreational opportunities in the GGNRA.


Note:  In support of our allegations that an appropriate evaluation of the plover at Ocean Beach is overdue, the following is taken from an SF SPCA document published January 9, 1997.  "The San Francisco SPCA feels strongly that the Golden Gate National Recreation Area (GGNRA) should conduct an objective study of all the factors affecting the safety of snowy plovers at Ocean Beach; provide a detailed analysis of each, along with a complete list of potential corrective actions; and submit a plan for protecting the birds for public review and comment. After taking the publics views into consideration, the GGNRA should then respond with a final plan explaining which corrective actions they chose, and why."


Conduct:  This study exhibits bias in its conduct as well.  Clearly, the participants who performed the surveys either had a pre-existing bias to construe the activity of dogs as harassment, or the training provided by Daphne Hatch and her staff created that bias in the participants.  Most likely it is a combination of both, as those individuals who volunteered to do these surveys are identified as Golden Gate Audubon Society members.  (We should point out that the Golden Gate Audubon Society is on the record as opposing any off-leash recreation in the GGNRA).  Ms. Hatch, in her introduction, spells out the definition of harassment per the Endangered Species Act (ESA).  Harassment is “an intentional or negligent act or omission which creates the likelihood of injury to wildlife by annoying it to such an extent as to significantly disrupt normal behavioral patterns which include, but are not limited to, breeding, feeding or sheltering”.  Ms. Hatch seems to use the terms harassment and disturbance interchangeably in this report, so we will generally refer to it as harassment/disturbance.  Harassment/disturbances are not well defined in the portion of the study where they are enumerated for Ocean Beach.  However, in the Crissy Field portion, there is more description provided for the harassment/disturbances observed.  In one case, harassment/disturbance of a plover by a dog was described as “alert posture – stood up and increased vigilance” (in other words, the plover lifted his head up and looked around).  Compare this “disturbance” that was classified by a volunteer and the authors of this study as an incident of harassment to the definition of harassment as provided by the ESA.  They are clearly inconsistent.  In this study, the authors and participants classified activity as harassment/disturbance that does NOT meet the definition of harassment provided by the ESA.  This is a classic example of examiner bias in the conduct of this study.  This is more precisely identified as “misclassification” and serves to invalidate the data collected and conclusions drawn in this study.


Analysis:  Analysis of this data is compromised because the data itself is in question.  Another factor that makes analysis of this data practically impossible is “confounding” in the design of this study.  In this case, “confounding” refers to the fact that this study is not designed to isolate the effect of each component of the beach environment that can affect the plover adversely.  For example, an off-leash dog is running at the waterline with its owner and they are some 20 feet from a plover.  There is additionally a raven 30 feet and closing from the plover.  The plover flushes, and it is recorded as a “disturbance”.  How is it apparent to the observer whether the dog, the owner or the raven was the source of the disturbance?  Practically, it could be any combination of all three.  Based upon the premise of this study, it is reasonable to assume the disturbance/harassment would be attributed to the off-leash dog.  Is that legitimate?  There does not appear to be any attempt made to isolate all other activities within the Park that may adversely affect the plover—they are merely given mention.  These would include:  Beach patrols in vehicles on the beach, equestrian use of the beach, people walking or jogging, kite flying, littering which attracts predators, the predators (usually ravens) themselves, and removal of kelp or driftwood which are sources of food.  No mention is even made of bonfires, camping, litter such as cigarette butts, or the shadows surfboards cast.


Perhaps the most egregious omission in this report is that there is no mention made of beach width. The beach width at Ocean Beach has been decreasing due to erosion.  Daphne Hatch’s 1996 report concluded on page 10: “Factors other than the number of people or dogs, possibly beach slope and width, appear to exert greater influence over Snowy Plover numbers on Ocean Beach”.  The GGNRA is quite aware that the number of plovers on Ocean Beach is not directly related to the number of people or dogs present on the beach.  However, in this 2006 Daphne Hatch report there is some discussion on page 8 that the plover numbers have leveled off since 2003, and have never matched the level they reached of 85 in 1994.  Concurrently, this report discusses repeatedly that since the reinstatement of off-leash recreation, the number of dogs at Ocean Beach has increased dramatically.  The report directly asserts the increase in dogs at Ocean Beach is responsible for a greater number of plover disturbances and it is inferred indirectly responsible for the diminished number of plovers.  Had Daphne Hatch been intellectually honest, she might have drawn the following conclusion from this data and a study she cites in this report, “Disturbance to wintering western snowy plovers", by K.D. Lafferty.  This Lafferty report states “The distance between human activity and the roost peaked at about 30 meters and relatively few people or dogs beyond this distance disturbed plovers”…presumably because a narrow beach increased the potential overlap between beach users and snowy plovers”.  Ocean Beach suffers from serious erosion, and hence the beach width has narrowed dramatically, especially during high tides.  It could more reasonably be concluded that the narrowed beach width is directly responsible for both the lower plover numbers and the increased frequency of perceived harassment/disturbance of the plover, not the greater number of dogs or their activities on or off of a leash.  The narrowed beach width has both eliminated much of the potential habitat for the WSP at Ocean Beach (this is consistent with USFWS critical habitat designation in 2005), and forced all occupants of the beach into closer proximity to the plover, thereby perhaps causing greater harassment/disturbance levels (especially if you construe lifting your head and looking around as a disturbance).


How great are the harassment/disturbance levels really?  The way the data is presented in this report is misleading. To put the data in its’ simplest form, in 2004 when dogs were required to be on-leash at Ocean Beach, one dog was observed harassing/disturbing a plover in 5.5 hours of observation on weekdays, and one dog was observed harassing/disturbing a plover every 2.5 hours on the weekends.  In 2005, when dogs were legally allowed off-leash on Ocean Beach, (and there were many more dogs present) 1 dog harassed/disturbed a plover in 2.4 hours of observation on weekdays, and fewer than 2 dogs harassed/disturbed a plover every hour on weekends.  Is this really significant?  This report gives us no data regarding the rate of disturbance from any other source, however, the number of ravens far exceeds the number of dogs out at Ocean Beach, and it can easily be concluded the harassment/disturbances due to dogs are dwarfed by the number of harassment/disturbances from the plover’s natural predator, the raven.


It is difficult for me to do further analysis of the data, because the GGNRA has illegally withheld the raw data from me.  In April of 2006, I requested, by means of a Freedom of Information Act request, all of the data/reports/Environmental Assessments the GGNRA had to substantiate their claim that there were resources in the Park that required protection. The GGNRA responded in writing that such data did not exist.  Based upon the representations made in the November 2, 2006 Memorandum from Daphne Hatch and GGNRA Head Ranger Yvette Ruan, the last of the data for this report was collected in February and March of 2006.  The data could and legally should have been provided to me in April of 2006.  I subsequently appealed this FOIA request to the DOI, and it has not been acted upon despite the fact that the time allowed by law for response has long since expired.  The DOI tells me I can sue them for it. 


Conclusion:  Rational analysis of the situation would suggest that the GGNRA is really not trying to solve a problem.  The GGNRA is merely interested in restricting dogs to leashes throughout the GGNRA.  Additionally, when taking into account Ms. Hatch’s above comments to the S.F. Chronicle in 2005, one must question the future of both humans and dogs in the GGNRA. Taking into account the data regarding the numbers of dogs chasing either shorebirds or plovers in context of the frequency of the behavior over time, it seems ticketing of the miniscule number of offenders would be appropriate rather than punishing all for the transgressions of a very few.  It is a bit like forcing all cyclists in the GGNRA to ride with training wheels because a very few speed through the park.   


If GGNRA management complains that they do not have the resources to adequately police Ocean Beach then it provides an appropriate reason to move for reversion of this property.  I remind you again of Rolf Diamont’s (GGNRA Environmental Coordinator circa 1975) conclusions when the GGNRA had just accepted possession of Ocean Beach from the City of San Francisco—Ocean Beach: no rules should be enforced here. Ocean Beach is too large and too accessible to control dogs.  It would be a logistical nightmare for the Park Service to try”. 


The Hatch report does not meet the criteria for a valid scientific study. It is more appropriately classified as “junk science”— “a publication that has the tone and trappings of science, but is so fundamentally and demonstrably flawed as to lack any serious claim to credibility”.  Junk science should never be used as the basis for establishing public policy.