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Comment on Balmford et al. (2009)

Posted by pergams on 18 Sep 2009 at 13:42 GMT

Balmford et al. [1] misrepresent our work [2,3] in several ways:

1. Our analyses and results were limited to the US & Japan. Our results for these countries are generally corroborated by the authors. We hypothesized that these trends in the US & Japan might be generalized to other rich, developed countries with large tracts of natural areas [2]. We do not hypothesize that these trends may be generalized to LDCs or to lands with few natural areas. However, the authors seem to insinuate otherwise. Indeed, another country matching our criteria of being rich and developed and having large tracts of natural areas (Australia) is also shown by the authors to have declining nature interest.

2. The authors state we did not show US camping and other hunting to be in downtrends, but this is not correct: our results show they are indeed in downtrends [2].

3. The authors state that videophilia is a plausible cause of declining nature interest, but that evidence is sparse. However, they do not cite or discuss our paper showing that videophilia is indeed a likely proximate cause for decline in US national parks visitation [4].

4. The authors hypothesize that many formal protected areas in richer countries are becoming increasingly crowded and thus less attractive to mature enthusiasts. We disprove this hypothesis for US national parks [4], however the authors do not cite or discuss this paper.

A key piece of our research has been to evaluate the implications of nature participation trends for biodiversity conservation. The authors state that falling visitation is mostly restricted to a few well-off countries, and that PA visitation is generally growing, but at a progressively lower rate (eventually falling below zero) with rising affluence. If correct, these findings do not negate our concern that disconnect with nature is potentially causing later disinterest with conservation in rich, developed countries with large tracts of natural areas; rather our concern is reinforced by the authors’ corroboration of trends in the US & Japan, and addition of Australia. If it is true that individuals from the wealthiest nations (sources of large donors and substantial global conservation funding) are spending less time in nature, then we are seeing a trend of great concern for biodiversity conservation.

The authors hypothesize that increased foreign ecotourism to LDCs may be responsible for the trends found. This hypothesis seems plausible to us, especially in view of a negative correlation with local affluence, and worthy of further examination. However, though a foreign ecotourism hypothesis is plausible we have substantial concern over its ramifications for the credibility of this study. The authors show that visitation and in some cases per capita visitation is rising in some countries, but the relative scale of declines and increases remains an important unknown. What proportion of the global nature recreation pie is represented? A 4% increase in Madagascar PA visitors is likely to reflect many fewer people than a 1.5% decline in Canadian PA visitors. In our paper we presented a pie chart reflecting the relative market share of each of our outdoor recreation variables [2]. It would be useful and informative for the authors to do the same with their data. For example in the US, foreign ecotourism is miniscule compared to natural areas visitation, camping, fishing, or hunting. The authors may well be comparing very minor increases in visitation in other countries due to foreign ecotourism with very major decreases in other forms of nature visitation. If so, they are merely documenting a minor countertrend, and may be misrepresenting their results by not publishing relatively small outright values.

On a related note, we agree strongly with comments in a concurrently published opinion piece [5] regarding relative data quality: "Pergams and Zaradic [2], for example, also sought data from countries such as Australia. They were sent data from two of eight states, one of which did not actually record visitor numbers—the figures were purely estimates. Australian tourism lobbyists quote park visitation estimates derived from very general off-site surveys of people's holiday intentions, carried out by the federal tourism agency. Such surveys are highly unreliable [2]. Even in face-to-face interviews with people who know you have been watching them, many report their own very recent actions inaccurately [6]. On-ground counts show the tourism surveys are inflated by 20–1,000% [7]. So, it's hard to measure small changes reliably" [5]. We were very explicit in our paper about our criteria for utilizing data, so that we would compare data of approximately equal quality and appropriateness (in other words, compare apples of equal ripeness rather than ripe apples and green oranges). We suggest that reliable results depend on using comparable data.

Ultimately, tracking visitor trends to PA is of interest primarily as a proxy for some of the more complex forces driving conservation that are much harder to quantify such as the cultural and political value placed on wild spaces. Global conservation efforts require understanding nature use trends and values on a relative scale in a global market. Testing the hypothesis that increased foreign ecotourism to LDCs is responsible for the trends found in the reported study is a valuable pursuit but requires comparable data of greater quality and equivalency than appears to be currently available. Comparing percent changes in visitation as equivalent units among nations varying greatly in population size and scale is likely to be both inaccurate and potentially misleading.

The trend of declining nature participation in the US and Japan reported in our work and further corroborated by the authors’ results is worrisome for global biodiversity conservation funding. Foreign nature-based tourism may be a short-term economic boon for less developed nations, as the authors suggest. However, if a larger global trend of disinterest with nature recreation continues, especially among the most affluent donor nations, then the long-term result for global biodiversity conservation is likely to be a bust.

Oliver R. W. Pergams & Patricia A. Zaradic
Red Rock Institute, Inc.

Literature Cited

1. Balmford A, Beresford J, Green J, Naidoo R, Walpole M, et al. 2009 A Global Perspective on Trends in Nature-Based Tourism. PLoS Biology 7(6): e1000144. doi:10.1371/journal.pbio.1000144.

2. Pergams ORW, Zaradic PA. 2008. Evidence for a fundamental and pervasive shift away from nature-based recreation. Proceedings of the National Academy of Sciences US 105:2295-2300.

3. Pergams ORW, Zaradic PA. July 8, 2008. Reply to Jacobs and Manfredo: More support for a pervasive decline in nature-based recreation. Proceedings of the National Academy of Sciences USA, 10.1073/pnas.0803331105.

4. Pergams ORW, Zaradic PA. 2006. Is love of nature in the US becoming love of electronic media? 16-year downtrend in national park visits explained by watching movies, playing video games, internet use, and oil prices. Journal of Environmental Management 80:387-393.

5. Buckley R. 2009. Parks and Tourism. PLoS Biol 7(6): e1000143. doi:10.1371/journal.pbio.1000143.

6. Littlefair C, Buckley RC. 2008. Interpretation reduces ecological impacts of visitors to World Heritage Areas. Ambio 37: 338–341.

7. Buckley RC. 2004. The effects of World Heritage listing on tourism to Australian national parks. Journal of Sustainable Tourism 12:70–84.

Competing interests declared: Our comment responds in part to criticisms of our work Pergams & Zaradic (2008).

RE: Comment on Balmford et al. (2009)

rnaidoo replied to pergams on 02 Feb 2010 at 20:00 GMT

Pergams and Zaradic state in the Comment above that we misrepresent [1] their work, however we reject this assertion. Their claim that conclusions emanating from their research on shifts away from nature-based recreation [2] were restricted to rich nations with large tracts of natural areas stands in contrast to the content and tone of their previous work. A cursory glance at statements contained in both their published papers (e.g., ref. [2], p. 2299, col. 1, par. 2: "…there has been a fundamental and general national and potentially international shift in people's participation in nature recreation…"; ref [2], p. 2299, col. 2, par. 2: "The cultural shift away from nature recreation appears to extend outside of the U.S. to at least Japan…") and in the popular media (e.g., Scientific American, Feb. 5, 2008, "'It looks like, clearly from the Japan data, that this may be an international problem,' Zaradic says") suggests little attempt to highlight the limitations of their analyses and interpretations. In ref. [2], mention of restriction to countries "large enough and wealthy enough to use their national parks in similar ways as the United States" is made only in the fine print (Methods); no mention appears in the main text. In addition, there is no mention anywhere regarding restrictions to those rich countries with "large tracts of land". Pergams and Zaradic also claim we were incorrect in stating that hunting, hiking, and backpacking (which in our final text we mistakenly referred to as "camping") have not declined in the last ~20 years, however this is in fact true (ref. [2], hunting: p. 2296, col. 1, par. 1; hiking and backpacking: p. 2297, col. 1, par. 1).

We certainly agree with Pergams and Zaradic that evidence of an increasing disconnect from nature is cause for concern on a number of fronts related to conservation. Where we and others [3,4] disagree is the strength of evidence for such a phenomenon and the methods and interpretations that to date have been offered as support. Pergams and Zaradic imply that the data set we have assembled is inadequate and question the credibility of our results because we have not quantified the entire global nature recreation pie, and because positive trends in developing countries like Madagascar might be swamped by negative trends in developed countries like Canada. We believe this opinion stems from a rather narrow, USA-centred view on trends in nature-based recreation, which they state are "…of interest primarily as a proxy for some of the more complex forces driving conservation…". In our view there are many more reasons to track trends in nature recreation. One of these is exploring the heterogeneity that exists in visitor rates across different ecological and socioeconomic contexts; even our limited analysis has shown that a one-size-fits-all explanation as advocated by Pergams and Zaradic does not pass muster when confronted with a larger and more geographically diverse dataset than their own. Tracking visits to protected areas also helps us understand the value of the ecosystem services offered by these places. The financial flows generated by nature-based tourism reflect an important source of funds for conservation in the developing world [5,6]. Understanding the direction and variability in trends of foreign exchange derived from international visitors to protected areas across the world is therefore of considerable importance for global conservation policy. As we state in our article, the data required for this purpose are surprisingly scarce, which is why, contrary to Pergams and Zaradic, the accompanying Primer in PLoS Biology duly recognizes that our new dataset is "…of enormous importance to conservation worldwide" [4].

Finally, Pergams and Zaradic object that we did not discuss their paper on videophilia [7], which gives us the opportunity to do so now. We believe this paper contains substantial errors in statistical methodology. The pitfalls of (i) attributing causality from interpreting complex phenomena affected by multiple interacting variables through simple univariate correlational analysis, and (ii) including highly collinear variables in multiple regression analysis, are very well known (e.g., ref [8]). Despite this, Pergams and Zaradic make causal interpretations from limited correlational analyses (e.g., p. 391, col. 2, par. 2: "Again we must note that the prevalence of home video games and internet use essentially came into existence around the time park visitation started declining, and feel this increases the likelihood of causality to some extent."). The perils of their approach to variable selection and model development are exposed in Table 2 of ref [7] (p. 391), which shows the results of a multiple regression model of national park visits. The strongest predictor variable, hours of internet use, has flipped from an apparently strong negative correlate of recreation trends when examined in isolation (p. 390, col.1, par. 4; Spearman's r = -0.783, P < 0.001) to being strongly positively correlated with nature-based recreation (Table 2, Std. coeff. = 1.794, t = 4.444, P = 0.0012). In other words, after controlling for the statistical effects of oil prices and other variables of interest, increased hours of internet use corresponds to increased, not decreased, visits to protected areas. This result is clearly at odds with the authors’ videophilia hypothesis, but they do not discuss it. Similar problems lead us and others [4] to be skeptical of their claims of "disproving" the hypothesis that crowding in United States parks is at least partly responsible for apparent declines in nature-based recreation.

Rather than attacking research that suggests conclusions that differ from their own [1,3], we suggest that Pergams and Zaradic focus on their own tests of an interesting but weakly-supported hypothesis on declining trends in nature-based recreation in some richer countries, and their attendant implications for conservation.

Robin Naidoo
Andrew Balmford
Andrea Manica

1. Balmford A, Beresford J, Green J, Naidoo R, Walpole MJ et al. (2009) A global perspective on trends in nature-based tourism. PLoS Biol 7(6): e1000144. doi:1000110.1001371/journal.pbio.1000144.
2. Pergams ORW, Zaradic P (2008) Evidence for a fundamental and pervasive shift away from nature-based recreation. PNAS 105: 2295-2300.
3. Jacobs MH, Manfredo MJ (2008) Decline in nature-based recreation is not evident. PNAS 105(27): E40.
4. Buckley R (2009) Parks and Tourism. PLoS Biol 7(6): e1000143.
5. Walpole MJ, Leader-Williams N (2001) Masai Mara tourism reveals partnership benefits. Nature 413: 771.
6. Hawkins DE, Lamoureux K (2001) Global growth and magnitude of ecotourism. In: Weaver DB, editor. The encyclopedia of ecotourism. Oxon, UK: CABI International. pp. 63-72.
7. Pergams ORW, Zaradic PA (2006) Is love of nature in the US becoming love of electronic media? 16-year downtrend in national park visits explained by watching movies, playing video games, internet use, and oil prices. J Environ Manag 80(4): 387-393.
8. Draper NR, Smith H (1998) Applied regression analysis. 3rd ed. New York: Wiley-Interscience.

No competing interests declared.