Showing posts with label environment. Show all posts
Showing posts with label environment. Show all posts

Friday, October 26, 2018

Do the economics and logistics of field ecology bias our understanding of environmental problems?

Location of Antarctic field stations. Image from Wikipedia.


Field ecology is difficult, time-consuming and expensive. Ecologists need to make decisions about where to do research, and if research questions focus on remote locations, there are likely a lot of constraints limiting options. For example, if research requires work in the Antarctic, odds are you'll be working at one of a few locations on the coast which, depending on the nature of the research, could bias our understanding of ecological or geological processes operating there.

The research needed for some questions can literally occur almost anywhere without much worry about how local context biases findings. That's not to say that local context will not play a role in ecological dynamics, and we should always be mindful of how local conditions influence the processes we are interested in. However, some questions are sufficiently general that we could envisage running an experiment in our backyard. However, there are research questions that necessitate careful consideration of the geographical location of research.

This is especially true for questions that pertain to the consequences of environmental change on ecological systems. The drivers of environmental change, whether it be pollution, nutrient deposition, changing temperature, extreme weather events or changes in precipitation patterns, all vary across the Earth and their impacts are similarly unequal. We shouldn't expect that a 2 degree C increase in average temperature to have the same effect in the tropics as, say, the arctic.

Location of Nutrient Network sites used in Borer et al. 2014
For some research endeavors, the solution to ensuring geographical coverage has been to replicate studies around the world. Take for example studying the effects of nutrient deposition in grasslands. There is a long history of ecologists adding nitrogen, phosphorus, and other nutrients to grasslands at specific locations in short duration experiments. These studies can tell us about how plant dominance might change, but it is difficult to extend this research to other locations facing different nutrient change patterns or that are inherently structured differently. The solution to this shortcoming is best represented by the globally distributed Nutrient Network experiment. The global experiment includes dozens of sites around the world that all replicate a basic set of experimental applications of plant nutrients, which has resulted in some very influential papers about global change effects on grasslands (e.g., Adler et al. 2011, Borer et al. 2014, Seabbloom et al. 2015).

This issue of the geography of research biasing our understanding of the impacts of global change is especially true for understanding the consequences of climate change in the Arctic. This was highlighted superbly by Metcalfe and colleagues recently (Metcalfe et al. 2018). They showed that most of the terrestrial ecology research in the Arctic has occurred in just a few places. And while this work has been extremely impactful and important for understanding the ecology of Arctic systems, they are not located in places undergoing the most drastic changes in climate. Therefore, because of the geographical location of research, we might not have a very good understanding of the impacts of climate change on Arctic ecosystems.

Where research is being done in the Arctic. Panel 'a' shows where publications are coming from and 'b' shows the impact in terms of number of citations (from Metcalfe et al. 2018).
This shows where photosynthesis has changed the most, which does not correspond well to where the research has been done (from Metcalfe et al. 2018).


This type of mismatch in climate change and research requires that ecologists purposefully establish research sites in areas that are rapidly changing. Metcalfe and colleagues suggest that the governments of Arctic nations establish focused research funding to support and promote research in these regions. This of course requires government dedication. The reality is it is cheaper and more efficient to do more research in existing, well supplied, field stations. Arctic scientists and professional organizations need to lobby environment or research government departments, and this research gap is an opportunity for Arctic governments to cooperate and share research costs.


References
Adler, P. B., E. W. Seabloom, E. T. Borer, H. Hillebrand, Y. Hautier, A. Hector, W. S. Harpole, L. R. O’Halloran, J. B. Grace, T. M. Anderson, J. D. Bakker, L. A. Biederman, C. S. Brown, Y. M. Buckley, L. B. Calabrese, C.-J. Chu, E. E. Cleland, S. L. Collins, K. L. Cottingham, M. J. Crawley, E. I. Damschen, K. F. Davies, N. M. DeCrappeo, P. A. Fay, J. Firn, P. Frater, E. I. Gasarch, D. S. Gruner, N. Hagenah, J. Hille Ris Lambers, H. Humphries, V. L. Jin, A. D. Kay, K. P. Kirkman, J. A. Klein, J. M. H. Knops, K. J. La Pierre, J. G. Lambrinos, W. Li, A. S. MacDougall, R. L. McCulley, B. A. Melbourne, C. E. Mitchell, J. L. Moore, J. W. Morgan, B. Mortensen, J. L. Orrock, S. M. Prober, D. A. Pyke, A. C. Risch, M. Schuetz, M. D. Smith, C. J. Stevens, L. L. Sullivan, G. Wang, P. D. Wragg, J. P. Wright, and L. H. Yang. 2011. Productivity Is a Poor Predictor of Plant Species Richness. Science 333:1750-1753.

Borer, E. T., E. W. Seabloom, D. S. Gruner, W. S. Harpole, H. Hillebrand, E. M. Lind, P. B. Adler, J. Alberti, T. M. Anderson, J. D. Bakker, L. Biederman, D. Blumenthal, C. S. Brown, L. A. Brudvig, Y. M. Buckley, M. Cadotte, C. Chu, E. E. Cleland, M. J. Crawley, P. Daleo, E. I. Damschen, K. F. Davies, N. M. DeCrappeo, G. Du, J. Firn, Y. Hautier, R. W. Heckman, A. Hector, J. HilleRisLambers, O. Iribarne, J. A. Klein, J. M. H. Knops, K. J. La Pierre, A. D. B. Leakey, W. Li, A. S. MacDougall, R. L. McCulley, B. A. Melbourne, C. E. Mitchell, J. L. Moore, B. Mortensen, L. R. O'Halloran, J. L. Orrock, J. Pascual, S. M. Prober, D. A. Pyke, A. C. Risch, M. Schuetz, M. D. Smith, C. J. Stevens, L. L. Sullivan, R. J. Williams, P. D. Wragg, J. P. Wright, and L. H. Yang. 2014. Herbivores and nutrients control grassland plant diversity via light limitation. Nature 508:517-520.

Metcalfe, D. B., T. D. Hermans, J. Ahlstrand, M. Becker, M. Berggren, R. G. Björk, M. P. Björkman, D. Blok, N. Chaudhary, C. J. N. e. Chisholm, and evolution. 2018. Patchy field sampling biases understanding of climate change impacts across the Arctic. Nature Ecology & Evolution 2:1443.




Seabloom, E. W., E. T. Borer, Y. M. Buckley, E. E. Cleland, K. F. Davies, J. Firn, W. S. Harpole, Y. Hautier, E. M. Lind, A. S. MacDougall, J. L. Orrock, S. M. Prober, P. B. Adler, T. M. Anderson, J. D. Bakker, L. A. Biederman, D. M. Blumenthal, C. S. Brown, L. A. Brudvig, M. Cadotte, C. Chu, K. L. Cottingham, M. J. Crawley, E. I. Damschen, C. M. Dantonio, N. M. DeCrappeo, G. Du, P. A. Fay, P. Frater, D. S. Gruner, N. Hagenah, A. Hector, H. Hillebrand, K. S. Hofmockel, H. C. Humphries, V. L. Jin, A. Kay, K. P. Kirkman, J. A. Klein, J. M. H. Knops, K. J. La Pierre, L. Ladwig, J. G. Lambrinos, Q. Li, W. Li, R. Marushia, R. L. McCulley, B. A. Melbourne, C. E. Mitchell, J. L. Moore, J. Morgan, B. Mortensen, L. R. O'Halloran, D. A. Pyke, A. C. Risch, M. Sankaran, M. Schuetz, A. Simonsen, M. D. Smith, C. J. Stevens, L. Sullivan, E. Wolkovich, P. D. Wragg, J. Wright, and L. Yang. 2015. Plant species' origin predicts dominance and response to nutrient enrichment and herbivores in global grasslands. Nat Commun 6.

Wednesday, August 30, 2017

INTECOL 2017: Building the eco-civilisation


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The International Association for Ecology holds their global INTECOL conference every 4 years, and it was recently held in Beijing, China. Given the location of this meeting, the theme was exceptionally appropriate: Ecology and Civilisation in a Changing World. I say that it was appropriate because no place embodies change more than China’s recent history, and I would argue that China is a prime candidate to benefit from ecological science.
One thing that was clear from the outset of the meeting was that China (both the scientists attending the meeting and the policy apparatus writ large) was serious about the notion of producing an ecological civilisation, or eco-civilisation. In 2007, the Communist Party of China adopted the idea of turning China into an eco-civilisation by incorporating ecological well-being into its constitution. In 2013, the Chinese government started implementing reforms that politically prioritised ecology and the environment. Most prominent of these was that local government officials and administrators were directed to no longer ignore the environmental consequences of development.
China is globally unique in its ability to institute change, literally with the stroke of a pen. Well documented is the ability for the major cities in China to implement drastic change in transportation policy by restricting who can drive when, and building public transit infrastructure at a torrid pace (see a commentary about this). The latest examples of cities’ power over transportation include the fact that electric cars are eligible to receive license plates immediate, while owners of conventional cars are required to wait years or spend tens of thousands of dollars to get their plates. The other example is the flooding of the market with public bicycles that can be parked anywhere and that require a phone app to unlock, and they literally cost cents to use.

A market flooded with a public bike-sharing program in China. These are all shared bikes, available everywhere, and they tend to congregate around bus stops (Photo by M. Cadotte).

I found it to be an interesting juxtaposition to see the multitude of bikes everywhere with the polluted sky that was apparent for the first two days of the conference. This was the very appropriate context for our conference. From the get go the theme of using the science of ecology to improve environmental management and policy seemed to underlie most of the talks and organised sessions. For most Chinese scientists, this is the context in which they work. To them, there is no real separation between human activities and nature, and the two have been intimately linked for millennia. The opening address was by HRH Charles Prince of Wales. Prince Charles eloquently commented on the importance of ecology in the coming decades, as humanity is testing the ecological bounds of the planet, and he encouraged attendees to use their research to affect change.

HRH Charles, Prince of Wales giving the opening address (Photo by M. Cadotte).

Representing the hosting organisation, Shirong Liu outlined all the important ecological advances in Chinese ecology, especially the development of extensive ecological experiments and research networks examining issues like climate change and nutrient deposition. Echoing Prince Charles’ call, Prof. Liu commented on the importance of ecology for Chinese policy, and the many recent policy changes in China, including the establishment of national parks, habitat restoration, climate change mitigation, and the greening of cities.
Given that most of China has been modified by humans, Gretchen Daily’s keynote address seemed incredibly poignant, even though the focus was on Costa Rica. She said that we’ve pretty much protected all the places that are likely to be protected as big parks, and that adding more is increasingly infeasible (China is an outlier). Instead, we should be looking to country sides and other human-dominated landscapes as the places to implement ecological principles to better manage these systems to benefit biodiversity and ecosystem functioning. These systems are where our science needs to pay off.

Evidence of ecosystem services in the Beijing Botanical Garden (Photo by M. Cadotte).
The talks throughout the conference echoed the themes of an ecology on and for human systems. I saw numerous talks from Chinese authors on understanding and managing human impacts, in systems from grasslands to lakes to cities. I participated in a panel discussion on how ecology could be used to create an eco-civilisation, and it was clear that there was a lot of optimism that the next decades will see a renaissance of ecology in policy, I was probably the least optimistic. I am doubtful that, having seen the United States pull out of the Paris Climate Change agreement, the political will can always be relied upon and creating an eco-civilisation depends on China’s ability to increase the standard of living without taxing ecological capacity more than it has. That said, there is currently a global leadership vacuum on the environment, created by political instability in Europe and the United States, and this is the time for China to be an environmental leader. 
Regardless, I saw inspiring talks on restoring ecosystems severely modified by human activity and invasive species, from speakers like William Bond, Carla D’Antonio, and Tom Dudley. I also ran an organised session on the importance of biodiversity in human dominated landscapes which covered topics from habitat fragmentation, to the ecology of cities, to the value of sacred groves in India for biodiversity.
After listening to talks at INTECOL 2017, one cannot help but feel that this is ecology’s time. We are entering an ecological era, and if ever there was a time to use our science to affect change, it is now.

Wednesday, June 21, 2017

What do we mean when we talk about the niche?

The niche concept is a good example of an idea in ecology that is continually changing. It is probably the most important idea in ecology that no one has yet nailed down. As most histories of the niche mention, the niche has developed from its first mention by Grinnell (in 1917) to Hutchinson’s multi-dimensional niche space, to mechanistic descriptions of resource usage and R*s (from MacArthur’s warblers to Tilman’s algae). Its most recent incarnation can be found in what has been called modern coexistence theory, as first proposed by Peter Chesson in his seminal 2000 paper.

Chesson’s mathematical framework has come to dominate a lot of discussion amongst community ecologists, with good reason. It provides a clear way to understand stable coexistence amongst local populations in terms of their ability to recover from low densities, and further by noting that those low density growth rates are the outcome of two types of processes: those driven by fitness differences and those driven by stabilizing effects that reduce interspecific competition relative to intraspecific competition. Many of the different specific mechanisms of coexistence can be classified in terms of this framework of equalizing and stabilizing effects. “Niche” differences between species in this framework can be defined as those differences that increase negative intraspecific density dependence compared to interspecific effects. If, as a simplistic example, two plant species have different rooting depths and so access different depths of the water table, then this increases competition for water between similar root-depth conspecifics relative to interspecific competition. Thus, this is a niche difference. Extensions on modern niche theory have offered insights into everything from invasion success, restoration, and eco-phylogenetic analyses.

But it seems as though the rise of 'modern coexistence theory' is changing the language that ecologists use to discuss the niche concept. When Thomas Kuhn talks about paradigm shifts, he notes that it is not only theory that changes but also the worldview organized around a given idea. At least amongst community ecologists, it seems as though this had focused the discussion of the niche to an increasingly local scale, particularly in terms of stabilizing and equalizing terms measured as fixed quantities made under homogenous, local conditions. A recognition of the role of spatial and temporal conditions in altering these variables seems less common, compared to the direction of earlier, Hutchinsonian-type discussions of the niche.

Note that this was not Chesson's original definition, since he is explicit that: “The theoretical literature supports the concept that stable coexistence necessarily requires important ecological differences between species that we may think of as distinguishing their niches and that often involve tradeoffs, as discussed above. For the purpose of this review, niche space is conceived as having four axes: resources, predators (and other natural enemies), time, and space.”

On a recent manuscript, an editor commented that the term 'niche processes' shouldn't be used to refer to environmental filtering since (paraphrased) “when ecologists refer to niche processes, they are usually thinking of processes that constrain species’ abundances locally, confer an advantage on rare species...” But is it fair to say that this is the only thing we mean (or should mean) when we discuss niches? I’ve had discussions with other people who’ve had this kind of response – e.g., reviewers asking for simulations to be reframed from niches defined in terms of environmental tolerances to things that fit more clearly into equalizing and stabilizing terms. That is a good description of a stabilizing process, which is termed a 'niche difference' in the modern coexistence literature. But there is still a lot of grey space we have yet to address in terms of how to integrate (e.g.) the effects of the environment (including over larger scales) into local 'niche processes' or stabilizing effects. It's a subtle argument - that we can use the framework established by Chesson, but we should try to do so without dismissing too-quickly the concepts that don't fit easily within it. In addition, elsewhere the niche is still conceptualized in varying ways from comparative evolutionary biologists who talk about niche conservatism and mean the maintenance of ancestral trait values or environmental tolerances; to functional ecologists who may refer to multidimensional differences in trait space; to species distribution modellers who thinks of large-scale environmental correlates or physiological determinants of species’ distributions. 

The niche is probably the most fundamental, yet vaguely–defined and poorly understood idea in ecology. So, formalizing the definition and constraining it is a necessary idea. And modern coexistence theory has provided great deal of insight into local coexistence and thus has allowed for a better understanding of the niche concept. But there is also a need to be careful in how quickly and how much we restrict our discussion of the niche. It's possible to gain both the strengths of modern coexistence theory as well as appreciate its current limitations. Modern coexistence theory isn’t yet complete or sufficient. It’s currently easier to estimate stabilizing and equalizing terms from experimental data in which conditions are controlled and homogenous, and this can inadvertently focus future research and discussion on those types of conditions. Models which consider larger scale processes and the impacts of changing abiotic conditions through space in time exist, but across different literatures, and these need continued synthesis. There is still a need to understand how to most realistically incorporating and understand the complex interactions between multiple species (e.g. Levine et al. 2017). The application of modern coexistence theory to observational data in particular is still limited, and such data is essential when species are slow lived or experimentally unwieldy. Further, when quantities of interest (particularly traits or phylogenetic differences) contribute to both equalizing and stabilizing effects, its still not clear how to partition their contributions meaningfully.
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Wednesday, November 16, 2016

The value of ecology through metaphor

The romanticized view of an untouched, pristine ecosystem is unrealistic; we now live in a world where every major ecosystem has been impacted by human activities. From pollution and deforestation, to the introduction of non-native species, our activity has influenced natural systems around the globe. At the same time, ecologists have largely focused on ‘intact’ or ‘natural’ systems in order to uncover the fundamental operations of nature. Ecological theory abounds with explanations for ecological patterns and processes. However, given that the world is increasingly human dominated and urbanized, we need a better understanding of how biodiversity and ecosystem function can be sustained in the presence of human domination. If our ecological theories provide powerful insights into ecological systems, then human dominated landscapes are where they are desperately needed to solve problems.
From the Spectator

This demand to solve problems is not unique to ecology, other scientific disciplines measure their value in terms of direct contributions to human well-being. The most obvious is human biology. Human biology has transitioned from gross morphology, to physiology, to molecular mechanisms controlling cellular function, and all of these tools provide powerful insights into how humans are put together and how our bodies function. Yet, as much as these tools are used to understand how healthy people function, human biologists often stay focussed on how to cure sick people. That is, the proximate value ascribed to human biology research is in its ability to cure disease and improve peoples’ lives. 


In Ecology, our sick patients are heavily impacted and urbanized landscapes. By understanding how natural systems function can provide insights into strategies to improve degraded ecosystems. This value of ecological science manifests itself in shifts in funding and publishing. We now have synthesis centres that focus on the human-environment interaction (e.g., SESYNC). The journals that publish papers that provide applied solutions to ecological and environmental problems (e.g., Journal of Applied Ecology, Frontiers in Ecology and the Environment, etc.) have gained in prominence over the past decade. But more can be done.


We should keep the ‘sick patient’ metaphor in the back of our minds at all times and ask how our scientific endeavours can help improve the health of ecosystems. I was once a graduate student that pursued purely theoretical tests of how ecosystems are put together, and now I am the executive editor of an applied journal. I think that ecologists should feel like they can develop solutions to environmental problems, and that their underlying science gives them a unique perspective to improving the quality of life for our sick patients. 

Wednesday, September 7, 2016

Where the wild things are: the importance of urban nature

Cities represent our ultimate domination over nature. They are landscapes that are completely modified to meet all of our needs and desires. In cities we drastically change the vegetation, reroute rivers, seal the Earth’s surface in impermeable cement, and often change the chemical composition of the air around us. For most people, this unnatural state of affairs seems completely natural. Its how we grow up.

What we don’t notice is all that is missing. The trees, the birds, and the mammals are largely absent from big cities. But not all cities are equal in this missingness. For those of us that live in cities like Toronto, Nashville, or Sydney, seeing birds and mammals is part of our normal life. In my back yard in Toronto, I am likely to see racoons, skunks, possums, red squirrels, eastern grey squirrels, chipmunks, deer mice, and a plethora of birds, and just down the road, foxes, coyotes, and deer are not uncommon. One morning I heard a ‘thud’ come from our sunroom window, and outside was a stunned red-tailed hawk (he was fine in the end). These cities are evidence that nature can persist and coexist with urban development.

However, there are other cities where nature is almost completely absent. While living in Guangzhou, China I saw just cats, dogs and rats, and barely any birds –shockingly no pigeons. Recently in while in Montpellier, France, it became obvious to Caroline and I (the two EEB & Flow contributors) that besides a small lizard species, pigeons and a few sparrows, we were not going to see any wildlife in the city. Guangzhou and Montpellier are very different cities in terms of size (16 million vs. 300 thousand), density, building height, pollution levels, etc.  But one way they are similar is that they are old. People have living and changing the landscapes in these regions for thousands of years. Of course the same could technically be said of North America and Australia, but the magnitude and intensity of human modification has no parallel in North America and Australia. Long-term intensive human activity removes other species in the long run. Is this the natural endpoint for our younger cities?

Cambridge, England. While quite beautiful, it is a typical old european city with a lot of stone.

Why we should celebrate raccoons

Toronto has a war against the raccoon. To most Torontonians, the raccoon is a plague –vermin that get into garbage cans and pull shingles off of roofs. Their density in Toronto is about 10 times higher than in wild habitats and many people in Toronto support removing them all together.

I have a different stance. We should be celebrating the raccoon. Yes raccoons cause problems; yes they carry disease; yes they damage property; yes their density is unnaturally high. But the same can be said of people (I don’t think I ever caught a flu from a raccoon). If raccoons were to recede to distant wilds and disappear from Toronto altogether, we would be no different than all those other cities where nature has completely lost. Raccoons give hope –hope that nature can flourish under the repressive and cruel dominion of urban centres. Raccoons remind us that nature has a place and can thrive in cities, and that we can share this world. They give me hope that Toronto’s destiny is not prescribed and we are not bound to the same fate as so many other cities.

I have a couple of new Chinese scientists visit my lab each year, and the differences between Toronto and say Beijing or Shanghai could not be more stark for them. To see deer, squirrels and raccoons in the city is a marvel. Every time one of these visitors comments on the wildlife in our city, I am reminded that we are really fortunate and have something that should be cherished.

Raccoon family –not an uncommon sight in Toronto (CCBYgaryjwood


Need to rethink urban nature

The problem is that Toronto, and most other cities, is continuing to grow and become more densely packed, making it more difficult for nature to endure. We need to rethink how cities grow and develop, and we need to keep a place for nature. There is no reason why new developments can't accommodate natural elements and green space –this often does not happen in most cities. Singapore is unique in this sense, new public infrastructure projects explicitly incorporate novel green space and infrastructure. I toured green sites there recently and saw a new hospital where it was impossible to tell where the park space ended and the hospital started (see picture below). There I saw patients tending gardens on the roof, nearby residents strolling through the forested courtyards, and turtles, wading birds and a large river monitor in the neighbouring pond. Also, Singapore's new large pump house infrastructure that reduces flooding in the city has a full sloping lawn on the top that is used by picnickers. In most North American cities this type of building would be grey industrial cement with little other function than to house pumps.

Singpore's Khoo Teck Puat hospital -the world's greenest hospital? 

Large old cities devoid of wildlife need not be the natural endpoint for a city.  Smart development and accommodating nature needs to be woven into the tapestry of cities. Toronto’s raccoons are great, and I wouldn’t want to live in a Toronto without them.


Friday, May 6, 2016

What’s so great about Spain? Assessing UNESCO World Heritage inequality.

Some places are more valuable than others. We often regard places as being of high or unique value if they possess high biological diversity, ancient cultural artefacts and structures, or outstanding geological features. These valuable places deserve special recognition and protection. The sad reality is that when we are driven by immediate needs and desires, these special places are lost.

The natural world, and the wonderful diversity of plants and animals, is on the losing end of a long and undiminished conflict with human population growth, development, and resource extraction. We don’t notice it when there is ample natural space, but as nature becomes increasingly relegated to a few remaining places, we place a high value on them.

The same can be said for places with significant cultural value. Ancient temples, villages, and human achievement are too valuable to lose and we often only have a few remnants to connect us to the past.

In either case, natural or cultural, when they’re gone, we lose a part of us. That is because these special places tell us about ourselves; where we come from, how the world shaped us, and what unites all of humanity. Why did the world cry out in a united voice when the Taliban destroyed the Buddhas of Bamiyan in 2001, even though many of those concerned people were not Buddhist? The answer is simple –the expansion of Buddhism out of India along ancient trade routes tells us why many Asian nations share a common religion. They tell us about ourselves, the differences that interest us, and the similarities that bind us. The same can be said about the global outcry over the recent destruction of the ancient city of Palmyra by ISIS.

Before and after photos of the taller of the Buddhas of Bamiyan. Image posted by Carl Montgomery CC BY-SA 3.0.

Similarly, the natural world tells us about ourselves. The natural world has constantly shaped and influenced what it means to be human. Our desires, fears, and how we interact with the natural world are products of our evolution. If I flash a picture of a car to my 500-student ecology class, very few students, if any, screech in fear. But if I flash a photo of a hissing cobra or close-up of a spider, invariably a bunch of students squirm, gasp, or scream. Rationally, this is an odd response, since cars are the leading cause of death and injury in many western countries. Snakes and spiders kill very few people in Canada.

These special places deserve recognition and protection, and that is what the UNESCO World Heritage designation is meant to achieve. To get this designation for a site requires that countries nominate ones that represent unique and globally significant contributions to world heritage, and are adequately protected to ensure the long-term existence of these sites.  World Heritage sites are amazing places. They represent the gems of our global shared heritage. They need to be protected in perpetuity and should be accessible to all people. Though some I have visited seem like they are loved too much with high visitation rates degrading some elements of Heritage sites.

Examples of UNESCO World Heritage sites. A) The Great Wall of China. B) The Gaoligong Mountains, part of the Three Parallel Rivers of Yunnan. C) Angkor Wat in Cambodia. D) An example of a site that may be too loved -Lijiang in Yunnan. All photos by Shirley Lo-Cadotte and posted on our family travel blog -All The Pretty Places.

UNESCO World Heritage sites should also be representative. What I mean by this is that they should be designated regardless of national borders. Heritage sites are found on all continents across most countries –though a number of politically unstable countries (e.g., Liberia, Somalia, etc.) do not possess Heritage sites, likely because they lack the organization or resources to undertake the designation application process, and they lack the governance to ensure a site is adequately protected. But there are substantial differences in the number of World Heritage sites across nations[1]. Some countries, because of inherent priorities, national pride, resources or expertise, are better able to identify and persuade UNESCO that a particular place deserves designation.

The distribution of the number of UNESCO World Heritage sites across countries and the top ten.

Why do we see such disparity in the number of World Heritage sites -where many countries have few sites, and a few countries have many sites? This is a difficult question to answer, and to do so I took an empirical approach. I combined data on the number of sites per country with Gross Domestic Product (GDP)[2], country size[3], and country population size[4]. I then ran simple statistical analyses to figure out what predicts the number of Heritage sites, and identified those countries that are greatly over-represented by Heritage sites, and those that are very under-represented. A couple things to note, the best statistical models included variables that were all log-transformed, I excluded the World Heritage sites that spanned more than one country, and I did not include countries that did not have any Heritage sites. The data and R code have been posted to Figshare and are freely available.

All three of GDP, area, and population size predicted the number of World Heritage sites. It is important to note that these three country measures are not strongly correlated with one another (only moderately so). So, larger, richer and more populous countries had more World Heritage sites. This makes sense –big countries should contain more unique sites due to random chance and more populous countries tend to have longer historical presence of organized states, and so should possess more cultural relics (especially China). GDP is more difficult to assign a reason, but high GDP countries should have robust national parks or other bureaucratic structures that assess and protect important sites, making them easier to document and justify for UNESCO.  GDP is quite interesting, because it is the single best measure for predicting the number of Heritage sites, better than population size and area. Further, neither country density (population/area) nor productivity (GDP/population) are strong predictors of the number of Heritage sites.

The relationships between the number of World Heritage sites and GDP, area, and population. Note that the axes are all log-transformed.

While these relationships make sense, it is also clear that countries are not all close to the main regression line and some countries are well above the line –meaning they have more Heritage sites than predicted; as well as some below the line and thus having fewer sites. When I combine the different measures in different combinations and look for the best single statistical explanation for the number of World Heritage sites, I find that the combination including GDP and population size, and their interaction (meaning that population size is more important for high GDP countries) is the best. For aficionados, this model explains about 65% of the variation in the number of Heritage sites.

Now, we can identify those countries that are over or under represented by UNESCO World Heritage sites according to how far above or below countries are from the predicted line (technically, looking at statistical residuals).

The deviation of countries from the predicted relationship between the number of sites and GDP and population (and their interaction). The top 5 over-represented and under-represented countries are highlighted.


The top five over-represented countries are all European, which means that given their GDP and population size, these countries have more World Heritage sites than expected. At the other extreme, countries under-represented come from more diverse regions including Africa, the Middle East and Southeast Asia.

An interesting comparison to think about is Germany and Indonesia. Germany has more World Heritage sites than expected (residual = +0.61) and is a moderately sized, high GDP country. Let me say, I like Germany, I’ve been there a half a dozen times, and it has beautiful landscapes and great culture. However, does it deserve so much more World Heritage recognition than Indonesia, which has fewer sites than expected (residual = -0.63)? Indonesia has spectacular landscapes and immense biodiversity and great cultural diversity and history. To put it in perspective, Germany has 35 World Heritage sites and Indonesia has just 8.

To answer the question in the title of this post: what’s so great about Spain? Well, it not only has beautiful and diverse natural landscapes and cultural history, but it appears to have the infrastructure in place to identify and protect these sites. It's place at the top of UNESCOs relative (to GDP and population) ranking of the number of World Heritage sites means that Spain's natural and cultural wonders are in good hands. However, for the countries at the other end of the spectrum, having relatively few World Heritage sites probably is not a reflection of these countries being uninteresting, or that they have little to offer the world, rather it is something more alarming. These places lack the financial capacity or national will to fully recognize those places that are of value to the whole world. The problem is that the globally important heritage that does exist in these places is at risk of being lost. These under-represented countries serve as a call to the whole world to help countries not just identify and protect heritage sites but to aid these countries with infrastructure and human well-being that empowers them to prioritize their natural and cultural heritage.