Mixed messages on Marine Protected Areas

I can’t remember the details of the first scientific conference I ever went to - not even its name - but I know it was on marine conservation, in Cardiff, and that a couple of us undergrads had made the trek from Norwich with little idea what to expect. The keynote speaker was Bill Ballantine, some of whose work on Marine Protected Areas (MPAs) in New Zealand I’d read as research for an essay. I remember no details of his talk, other than it adding to my general opinion of MPAs as a Good Thing; more memorable was his (grumpy, admirable) single word response - “No” - to a lengthy question from the floor. Anyway, this came back to me recently when I saw a new paper from Ballantine, giving a 50 year New Zealand perspective on MPAs. In particular, he suggests that the struggle to convince people of the worth of MPAs elsewhere could be greatly reduced by using New Zealand’s long (and ultimately successful) experiment as an exemplar. As it happens, another eminent MPA researcher, Timothy McLanahan, has also just published an analysis of the effectiveness of Kenyan MPAs based on data going back almost as far. These long-term perspectives give some context to the latest marine planning developments in the UK, where we are slowly (too slowly according to many voiciferous campaigners, not least Hugh Fearnley-Whittingstall, whose latest Fish Fight aired last week) progressing towards a network of marine conservation zones (MCZs). Campaigners disagree with other marine stakeholders over how much evidence is needed in order to establish these MCZs, and tempers can get rather frayed (not helped by the use of the word ‘Fight’ in the campaign; see my post from last year) - although there has been a certain rapprochment over the last year (this fishing industry view, for example, seems quite conciliatory to me and is hardly ‘anti conservation’).

So any evidence about the effectiveness of MPAs is to be welcomed, and a new study by Graham Edgar and colleagues published recently in Nature provides the most comprehensive review to date. Let me say at the outset that this is an enormously impressive piece of work: the team surveyed almost a thousand reefs from 87 MPAs and another thousand or so non-protected sites, from 40 countries around the world, using a standard methodology, their coverage allowing systematic comparisons of protected and non-protected areas using neat statistical methods. Their decision to concentrate on reefs, and on reef fish in particular, was both sensible - in that most MPAs are on reef systems, and reef fish are especially well studied - and necessary in order for the study to be feasible. It seems almost churlish to note that the 8000 or so reef fish species constitute 3-4% of described marine species, and perhaps just 1% of all marine species; but it is important that we bear this in mind when interpreting their conclusions: we have far less quantitative data on the effectiveness of MPAs for the groups constituting the majority of marine biodiversity.

Nevertheless, the scope of this study was broad enough that certain generalisations emerged. In particular, the authors were able to identify five factors that are key to the conservation success of an MPA. (“Success” here is defined using various measures including numbers of all fish species, numbers of species in key groups such as sharks, biomass of all fish, and of large fish.) These factors they term NEOLI, for No take (no fishing allowed), Enforced (effective enforcement of regulations), Old (long-established), Large (in terms of the area protected), and Isolated (separated from similar habitat by an extent of deep water or sandy substrate). They found that MPAs possessing four or five of these attributes score markedly higher than non-protected areas, particularly for total fish biomass, large fish biomass, and shark biomass. But MPAs with one or two NEOLI characteristics only were ecologically indistinguishable from unprotected sites.

And here’s where the mixed messages begin, in terms of the effectiveness of MPAs as a conservation strategy. First, across their entire dataset only four MPAs had all five NEOLI characteristics. Just five more had four characteristics. In other words, although MPAs can be very effective at achieving conservation objectives for reef fish, hardly any actually are. And as the authors say, “The low proportion of MPAs possessing four or five NEOLI features (10%), and thus regarded here as effective, probably overstates the true proportion of effective MPAs worldwide. Our survey strategy deliberately targeted well-known and well-regarded MPAs, with most large and long-established MPAs included in this study.” This is sobering indeed.

But the second mixed message is rather more subtle. Many proponents of MPAs talk them up as ‘win-win’. That is, MPAs are good for both conservation and for fisheries, largely because fish populations can build up within a reserve and then ‘spill over’ to the surrounding area, where they can be fished. This is certainly an argument I've made in the past. Yet the ‘I’ of NEOLI stands for Isolation, precisely because Isolation avoids spillover, so that protected fish stay within the MPA - in other words, an Isolated MPA specifically excludes the “presence of continuous habitat allowing unconstrained movement of fish across MPA boundaries”, which is exactly what MPAs are supposed to deliver to surrounding fisheries. Thus, one of the major contributors to the success of an MPA in conservation terms, is that it does not benefit fisheries.

This is, I think, extremely pertinent to the current debate within the UK, where conservation outcomes of MPAs are often conflated with other potential outcomes. The danger here is that we end up with reserves that are suboptimal for all objectives. As in all conservation initiatives, it is much better to have specific, measurable objectives defined at the outset, so that the effectiveness of any intervention can be properly assessed. Scientific evidence has a key role in this planning process, and - frustrating as it feels - this can take time. Isn’t it worth taking just a bit more time now, to ensure our seas are properly - and effectively - protected for future generations?

Wild extrapolation and the value of marine protected areas

Last week, the UK National Ecosystem Assessment published a follow-on report on the value of proposed marine protected areas (rMPAs) to sea anglers and divers in the UK. This report gained a fair bit of coverage, likely because the headline numbers it proclaimed are quite astonishing: “The baseline, one-off non-use value of protecting the sites to divers and anglers alone would be worth £730-1,310 million… this is the minimum amount that designation of 127 sites is worth to divers and anglers”. Furthermore, they claim an annual recreational value for England alone of the rMPAs of £1.87-3.39 billion, just for these two user groups (divers and anglers). These numbers are so astonishing, in fact, that my bullshit klaxon went off loud enough to knock me off my chair. See, I’ve been thinking recently about sea angling as an ecosystem service, and so know that there’s estimated to be somewhere around 1-2 million sea anglers in the UK. The number of divers is, I reckoned, likely to be considerably lower (there’s a higher barrier to entry in terms of equipment, qualifications, etc.). So these headline figures imply an annual spend -  purely on their hobby - somewhere in the order of £1000 for every single self-declared sea angler or diver. Which seems rather on the high side, given that one would expect a very long tail of ‘occasional’ dabblers in each activity (e.g. people who spin for a few mackerel on holiday).

So, I bucked down and read the 125 page report, to find that the authors had done some things really nicely. Their valuations are based on online questionnaires featuring a combination of neat choice experiments, willingness to pay (WTP) exercises, and an valuable attempt to characterise the non-monetary value of the sea-angling or diving experience (things like ‘sense of place’, ‘spiritual wellbeing’, etc.). But the headline numbers are highly dubious (worthless, in fact), because they did a few things very very badly indeed. Unfortunately, they did a different bad thing for each of their two major monetary valuation methods, so the numbers emerging from each are equally dodgy, as a modicum of mental arithmetic, common sense, and ground-truthing will show.

First, the annual recreational value models are nicely done, using a choice experiment based on travel distances to hypothetical sites with different features to assess which of those features are most valuable. Mapping these features onto the rMPAs leads to a ranking of these sites in terms of how attractive they are to anglers and divers. One could quibble with details here - perhaps the major quibble would be that there is no ‘control’, i.e. no assessment of the value of sites which are not proposed for protection. But in general, I think this analysis gives a decent estimate of how the survey respondents value the different sites.

They then attempt to get an overall annual value for each site by multiplying its value to individuals by the number of visits it receives in a year. This is where the problem arises: attempting to generalise from these respondents to the entire population of anglers (estimated at 1.1-2 million) or divers (estimated at 200,000). I’m going to concentrate on the anglers because the issue is most extreme here: their models are based on 273 responses, a self-selected group of anglers acknowledged within the report to be especially committed (averaging 3-4 excursions a month) and interested in marine conservation, and representing between 0.01 and 0.02% of the total population, i.e. 1 or 2 responses per 10,000 anglers (they also a self-selected sample of highly experienced divers, representing around 0.5% of all divers, i.e. 5 per 1000). Extrapolating from this sample to the entire UK angling population produces some interesting results.

For example, using this methodology Chesil Beach & Stennis Ledges rMPA on the Dorset Coast has an estimated 1.4-2.7 million visits by sea anglers annually. That translates to 3800-7400 visits every single day of the year. Compare this to a (highly seasonally variable) average of around 3000 visits per month to Chesil Beach Visitors Centre. Or you could look at the Celtic Deep rMPA, a site located some 70km offshore, where they estimate between 145,000 and 263,000 angling visits per year. That’s 400-720 visits a day, which translates to approx 40-70 typical sea angling boats, each full to the gunwales every single day of the year. Of course, this is simply because the tiny sample is uncritically extrapolated. In the case of the Celtic Deep, it is straightforward to calculate that there were actually 36 observed visits, which (when divided by 273 and multiplied by 1.1 or 2 million) gives you 145-263,000 estimated visits. Using this logic, the minimum number of visits a site could receive is (1/273)*1.1 million, or >4000. Diving numbers are similarly unrealistic, with estimates of 123-205,000 visits a year (340-560 per day) by divers to Whitsand & Looe Bay, or 26-44,000 a year (70-120 per day) at Offshore Brighton, which is around 40km offshore.

This kind of wild, uncritical extrapolation is staggering, akin to using the opinions of a focus group of LibDem party activists to predict a landslide in the next election. It’s a textbook example of the utility of a bit of simple guesstimation (e.g. a million visits a year means 10,000 visits/d for 100 days, or ballpark 2500/d over the whole year), allied to some common sense (have you ever experienced those kinds of numbers when you’ve visited the UK coast?)

So, we can discount the big annual recreational value figures. What about the WTP exercise? WTP has its fans and its critics. My view is that it’s a useful way of ranking scenarios according to preference, but I don’t give a lot of credence to the ££ generated, simply because by increasing the number of scenarios you can quickly get people to commit more cash than they intended. But regardless of that, the authors of this report appear to have made a very strange decision in aggregating the WTP estimates arising from their questionnaire. They worded the questions very carefully, presenting each respondent with a single site, outlining its features, and asking how much they would be WTP as a one-off fee for its protection - being sure to think of this amount as a real sum of money, in the context of their household budget. These numbers are then used to give an average WTP for all the rMPAs, which seems reasonable, and a useful way to rank the sites.

But They then simply multiply these site level averages by the whole UK angling (or diving) population to get a total WTP for the whole set of rMPAs.

Think about what they’ve done there.

They’ve asked people how much they would be willing to pay to protect a single site, and have then assumed that the same person will pay a similar amount for every site in the network. So if you agreed that you’d be prepared to pay a one-off sum of £10 to protect a site, you could find yourself with a bill for over £1000 to protect the whole network. (This is a slight over simplification, as specific values are site-specific, but it is essentially what they’ve done.) You simply cannot aggregate WTP like this. I mean, I’m not an economist, but if economists think you can do this, they are deluded.

Again, a bit of common sense would have helped here. The authors compare this WTP to an insurance premium, which is a useful analogy. But how many anglers or divers are really, when it comes down to it, prepared (or even able) to shell out a £1000+ insurance premium to prevent damage to the marine environment which may or may not occur in the future?

Anyway, that’s what’s been bugging me these last few days. I could go on (for instance, on a more philosophical level, is replacing strictly regulated commercial fishing with unregulated recreational angling necessarily a good thing for the marine environment? Will diving or - especially - angling actually be allowed in these rMPAs?). And there are some useful things in the report. It confirms that people do value the marine environment, really quite highly, and that different features are valued differently by different groups - a useful starting point for some more focused research, and helpful in placing relative values on different rMPAs. But unfortunately - inevitably - media attention has focused on the ludicrous headline numbers, something the authors have actively encouraged in their framing of the report.

A final positive point to end on: my bullshit klaxon seems to be in fine working order.