Postprint of: Vanclay, J.K., 2001. The Effectiveness of Parks. Science 293:1007 (10 August 2001).
On the effectiveness of Parks
Jerome K Vanclay1
Bruner et al.2 examined the effectiveness of parks in the tropics, drawing on survey data to
support their contention that parks 1) have been effective; 2) need more support; and 3)
should remain a central component of conservation strategies. Their conclusions remain
equivocal.
They focused on 520 parks in areas categorised as “partly natural” or “human dominated”,
established at least 5 years, and exceeding 5000 hectares. “Directors of conservation
organizations and protected area agencies helped identify a representative” subset of 82 parks.
A further 5 of 15 conservation areas in Laos, and six parks from outside the original sphere of
interest were included in the study, bringing the total sample size to 93. A questionnaire was
used to gather information on conditions within and surrounding the park. Only one response
was obtained for each park. “Park managers or park staff constituted 56% of respondents…”.
Nine of the parks in the sample receive “some level of support from Conservation
International” (the organization that conducted the survey). Correlations suggest that the 11
supplementary samples and the nine CI-supported parks do not differ from the general trend
of park effectiveness (r = –0.16,P = 0.06 and r = 0.05, P = 0.3 respectively), but there is no
way to test for bias in the selection of a “representative” subset or amongst respondents
completing the survey. Respondents are not identified in the data file, so it is not possible to
examine if park managers differed from researchers in their views on park conditions. More
critically, it is not clear whether responses reflect respondent opinions, or whether a genuine
attempt was made to gauge the incidence of fire, clearing, grazing, hunting and logging within
and surrounding the parks. Because of these deficiencies, the data should be considered
anecdotal rather than substantive.
Bruner et al. presented analyses suggesting that the incidence of clearing, grazing and burning
is lower, and the abundance of game and commercial tree species is higher within parks than
in the adjoining 10-km wide surroundings. These differences are attributed to the
effectiveness of parks, but may be due to other factors (e.g., natural features and cultural
traditions that discourage disturbance). A more parsimonious suggestion is that apparent
differences may have always existed, or may be area-dependent (a 10-km buffer represents
twice the median park area). The data suggest that park creation tends to reduce clearing
and/or foster regrowth within the protected area (paired t=1.8, P=0.03), but do not offer
reliable insights into current clearing patterns because the survey employed different
categories for clearing within and surrounding parks (viz. 0, 1–5, 6–10, 11–20, 21–40, 41+%
and 0–10, 11–30, 31–50, 51–70, 71–90, 91–100% respectively).
Bruner’s index of park effectiveness involved rescaling the clearing data from 6 onto 4
categories. Re-scaling categorical data in this way involves subjectivity, results in a loss of
information, and is not necessary to examine correlations. I computed an alternative index of
effectiveness by averaging the (unadjusted) difference between values (of clearing, burning,
hunting, logging and grazing) reported inside and outside parks3. The resulting index offers
better insights into relative, but not absolute performance of parks (i.e., if all risks are equal,
with 8% clearing both within and surrounding a park, my index will be [3–1 +bi–bo +hi–ho
1 Southern Cross University, PO Box 157, Lismore NSW 2480, Australia. Jvanclay@scu.edu.au
+li–lo +gi–go]/5 = 0.4 because clearing has different scales). My assertion that responses
denoted “not applicable” and “not available” both denote missing values, resulted consistently
in fewer degrees of freedom than reported by Bruner et al. Rather than use Spearman’s rank
correlations, I plotted all the possible predictors against park effectiveness and selected
appropriate transformations to linearize any trend. Correlations obtained in this way differ
substantially from those reported in Table 2; significant correlations and selected departures
from Bruner’s findings are reported in the table below. It is noteworthy that a park’s budget
(whether total, national or donor; its recent increase or decrease; and whether absolute or per
unit area) is not significantly correlated with effectiveness in this study or in Bruner’s study.
Predictor variable Transform r P n Bruner’s
rs
Local Educators per 100 km2
Area under contested ownership
Demarcation of border
Guards per 100 km2
Log(X+1)
—
—
Log(X+1)
0.35
–0.31
0.28
0.27
0.003
0.008
0.01
0.02
60
56
59
56
—
–0.15
0.21
0.27
Logging deterrent
Clearing deterrent
Compensation for damage
Budget
Legal inhabitants
Years established
Sqrt(X)
Sqrt(X)
—
Log(X+1)
Log(X+1)
Log(X)
0.19
0.24
0.05
–0.02
–0.20
–0.01
0.1
0.07
0.4
0.5
0.07
0.5
46
35
57
33
53
66
0.24
0.27
0.20
–0.01
—
—
The data in the table above are not orthogonal, and several variables seem to reflect the same
trend (e.g., the correlation between local educators and guards is 0.58). A stepwise regression
approach suggests that only two variables are relevant, local educators and demarcation:
Effectiveness = 1.7 Log (L.edu+1) +0.2 Demarc –0.25
where L.edu is the number of local staff (full-time equivalents per 100 km2 of park area)
working primarily on educating and building awareness in local communities about the park’s
goals and mission, and where Demarc has six categories (0–10, 11–30, 31–50, 51–70, 71–90,
91–100%) indicating the percentage of the park border that is clearly identifiable. Standard
errors for these parameters are 0.5, 0.06 and 0.25 (P<0.001, P=0.001, P=0.3) respectively.
This implies that parks are more effective if local people know that they are there, and know
why they are there. It supports the contention that tropical parks are effective, and that
differences within and surrounding parks may be due to the establishment of a protected area.
It is regrettable that the anecdotal nature of the underlying data detracts from this finding
To conclude:
The evidence in support of Bruner’s first conclusion is equivocal. In the opinion of
respondents, conditions within parks are better than in their surrounds. Parsimony begs
whether these apparent differences have always existed, or could be an artefact of sampling
(i.e., selection of the parks; design and conduct of the survey; comparing with surrounds
larger than the parks in question).
There is no evidence to support Bruner’s second conclusion that increased support will
improve effectiveness of parks. This lack of evidence prevails despite the fact that any
personal bias on the part of directors involved in selecting the sample, and managers involved
in completing the survey may have contributed to a more favourable (i.e., pro-park) result
than a more rigorous survey might indicate.
Bruner’s third conclusion remains untested. His data and analyses shed no light on the
relative efficacy of protected areas versus other conservation initiatives. Since both land and
financial support for conservation are limited, the issue is not whether parks are good, but
whether parks are better than the alternatives. There are several alternatives that could be
examined, but a 10-km band around a park is not an informative alternative. In terms of
conserving habitat, a better test would be a comparison of habitat quality within protected
areas versus that in community managed areas and in other multiple-use initiatives. In terms
of conserving species, a comparison of the performance (both in terms of success and cost) of
protected areas versus ex-situ conservation efforts may be more relevant.
1 A.G. Bruner, R.E. Gullison, R.E. Rice & G.A.B.da Fonseca, 2000, Effectiveness of Parks in
Protecting Tropical Biodiversity, Science 291:125-128.
2 My thanks to Aaron Bruner for providing a copy of his data and making this analysis possible.
