The Price of a Photo on a Camel Is All It Takes...

As a follow-up from my last post, I thought I'd share with you an image circling around the media that effectively sums up a lot of what I talked about. The last panel really struck me - globally, direct tourism carbon dioxide emissions (so not even including the indirect emissions embedded in food production, hotel construction etc.) are almost double those released by 5 of the top 10 emitting countries. So whaddya say? Would you be willing to pay the price of a photo on a camel to decarbonize tourism? 

Just a note that in the top panel, the 'decarbonized' scenario is based on the high-end emission reduction scenario (-70% by 2050) of the IPCC's recommended range (i.e. very, very, very positive... idealistic even, one might say.) If the scenario that's actually been endorsed by the tourism industry (-50% by 2035 and then stable) was shown, the graph may have been slightly less dramatic. Always best to take things the media says with a pinch of salt...

Source. Image is based on this study.

A survey conducted on tourists travelling to Churchill Bay in Canada found that 46% of those questioned were willing to buy carbon offsets on top of their flight ticket (and, in fact that the average price willing to be paid is 10% of the cost of that flight - far more than $11 in many cases!) However, they also found that a strong barrier purchase of carbon offsets was the doubt surrounding what a carbon offset is, how it works to mitigate against carbon emissions, and the most reliable companies to purchase them from. This suggests to me that climate change education is key in encouraging consumers to opt for carbon offsets, and critical in gaining customers sympathies if carbon offsets are imposed as a compulsory tax on airplane tickets.

Can the Tourism Sector Survive in a Decarbonized World?

In a couple of days time, the 21st session of the Conference of the Parties (COP-21) will be happening in Paris to agree upon a fresh global agenda restricting increases in average global temperature to 2°C relative to pre-industrial temperatures. Currently, the tourism sector globally is pretty much completely reliant on energy from fossil fuels. Direct emissions contribute an (highly conservative!) estimated 5% to global anthropogenic CO₂ emissions, more than all but 5 countries worldwide! Furthermore, one business as usual scenario (which even incorporates optimistic advances in energy efficiency) predicted tourism's CO₂ releases will increase by ~135% from 2005-2035 with an increase in travel numbers, frequency and distance largely from rapidly developing countries.

In order to have a likely (i.e. not even certain!) change of achieving COP-21’s target, the IPCC stated that current worldwide CO₂ emissions need to be lowered 40 - 70% by 2050. The United Nations World Tourism Organisation (UNWTO) has endorsed a sectorial carbon emissions reduction target of 50% by 2035 (relative to 2005 emissions). Put bluntly, the coordinated national and international policies required throughout the global tourism sector to achieve such emission reductions do not currently exist. In fact, none of the available decarbonization scenarios designed to achieve the 2 °C target even explicitly discuss tourism, despite its substantial contribution to global emissions. We shall wait with baited breath as to the outcome of the COP-21 negotiations, but the question remains regardless: how will the tourism sector survive in such a decarbonized global economy?

In this post I will compare the effectiveness of two distinct policy strategies tourism could take to reduce CO₂ emissions: carbon offsetting and emissions abatement.

Carbon offsetting or trading is a market-based mechanism which involves purchasing emission reduction credits achieved in sectors outside tourism. Although effectively avoiding the costs and any technological limitations of actual emission reduction, offsetting has so far been implemented with highly variable and non-standardised verification and credibility. Beyond problems of credibility, offsetting without legally binding emission reduction targets and caps for sectors can result in total global greenhouse gas emissions remain pretty much the same – essentially a business as usual scenario justifying continued inaction and attracting high levels of criticism from activists.

On the other hand, emissions abatement refers to explicit reduction of carbon emissions within the tourism sector, through mechanisms such as efficiency improvements to reduce energy usage and a transition to lower-carbon fuels. The potential for reducing tourism’s emissions is dependent on subsector, being especially expensive and tricky for air-travel as fuel efficiency advances and low-carbon fuel alternatives are both limited. Conversely, sizeable reductions in emissions (20 - 50%) are possible for the accommodation subsector at an initial negative cost as shown in Figure 1, via investment in energy efficiency, biofuels and renewable power.

Figure 1. A comparison of tourism sub-sector emission reduction and carbon offset prices with time. Source.

A recent paper modelled the financial costs of two emission reduction scenarios with either solely carbon offsetting, or offsetting in combination with abatement. Although the difference is slight, the results in Figure 2 show that emission abatement combined with offsets to strategically target aviation, is less expensive than carbon offsetting on its own, for both emission reduction scenarios. In fact, the additive cost throughout the thirty five years is 5.2% lower for the combination of abatement and offsetting (scenario 2) than scenario 1.

Figure 2. Cost of exclusive carbon offsetting, or offsetting combined with emission abatement for two emission scenarios: either a -50% reduction by 2035 (from 2005 levels) and subsequent stability, or a -50% reduction followed by a -70% reduction till 2050 after 2035. Source.

Importantly, in practical terms, the costs for emission reduction appear attainable as a proportion of overall global tourism revenue. Significant investment is required – starting at approximately US $1 billion annually beginning in the 2020s – but relatively speaking, this investment is lower than 0.1% of the predicted global tourism income for 2020. For example, if the projected costs for achieving scenario 2 by 2030 ($ 70 billion) was spread amongst the projected 6.6 billion domestic and international travellers for that year (under a medium growth projection for population), the per trip cost would be approximately US $11 - on par with many existing tourism fees and taxes set by governments and private companies that have had little, if any, impacts on the overall economic growth of thesector.

So what is your opinion, my curious reader? Is a global system of carbon trading the best way forward, investment in emissions reduction, or a combination of the two? And would you be willing to pay the extra $11 to carbon neutralise your holiday and ensure sustainability of the tourism industry? Personally, the path seems straightforward – beyond the comparative cost effectiveness of emission abatement with strategic carbon offsetting, future international agreements such as those expected at COP-21 may impose stricter emission and carbon trading limits for the tourism sector. Without investing in emission reduction now, this would leave the sector exposed to potentially increasing carbon trading costs and struggling to rapidly reduce emissions, hindering future economic growth of the sector.

Increased temperatures are really not in tourism's best interest. Many popular tourist destinations and activities, from the skiing industry to iconic species, are negatively affected by climate change. As could be expected, the modest $ 11 cost per traveller for the required investment has been widely shouted about in the media – almost exclusively in a positive light, with catchy slogans such as “are we willing to pay less than the price of an extra checked bag…?” and, my personal favourite: “the $11 solution to cleaning up the tourism business”. This is a good thing. Raising public awareness of the global environmental impacts of tourism and its potential management pathways is necessary. But the cost isn't the only thing to consider: emission reductions will not be easy. The tourism sector will require its own clear, globally integrated and consistent strategic policy framework that all subsectors and countries are on board with, combined with a sector-wide systematic emissions monitoring system. Without these, business leaders and investors will be unwilling to invest in low-carbon technologies for the sector, leaving it with little hope of achieving its emission reduction plans. Greater discussion and coordination amongst the tourism industry, governments and researcherss is necessary to address both of these challenges. The model discussed above assumed a well-functioning governance systems, yet this will not always be the case, especially in developing countries. Yet in light of the rising consumer activism against heavily carbon-emitting sectors, the global tourism industry will not be able to hide for long – it needs to make itself heard in international discussions such as COP-21, and it needs to start taking responsibility for its actions if it is to become truly sustainable.

BREAKING NEWS: KILLER SUNSCREEN MURDERS INFANT CORALS IN COLD BLOOD!

During my somewhat shameful evening routine of trawling through Daily Mail online, I came across a rather dramatic article on how sunscreen lotions are “killing off” coral reefs. Having previously explored the impacts of recreational tourist activity on coral reefs this immediately caught my attention. My initial thoughts were pretty sceptical – the language was highly sensationalist (posing sun lotions as an “existential threat”), and after all, it is the Daily Mail. But I eventually found the original, much more academic (and, I must say, rather dense) article that has since received heavy press coverage. Hence, not only am I able to further use my blog to name-and-shame tourism for killing off corals, but I was presented with a tantalising opportunity to compare the Daily Mail’s (and other news outlets) translation of hard academic science to, well, chain-procrastinators like me.

Oxybenzone is an chemical ingredient that shields against ultraviolet radiation, often present in sunscreen lotions. The specific oxybenzone studied in the article is benzophenone-3 (BP-3). An estimated 6 thousand - 14 thousand tonnes of sunscreen is released into areas surrounding coral reefs annually, both directly through swimmers, and indirectly through wastewater discharges from coastal development, e.g. hotel sewerage systems. Many of these lotions contain 1-10% BP-3, putting roughly 40% of coral reefs at exposure.

The experimental results of the study identified several toxicity mechanisms resulting from exposure of juvenile corals to BP-3, including DNA damage to coral larvae, reducing juvenile survival and resilience to other stressors, such as rising sea-surface temperatures under climate change. This changed the larvae of the coral species Stylophora pistillata from being healthy and mobile, to deformed and sessile - as shown in Figure 2. Furthermore, corals exhibited increased susceptibility to bleach at lower temperatures with rising concentrations of oxybenzone. 

Figure 2. Panel A is a healthy juvenile planula, approxiamtely 5 mm in length. Panel B is a sessile deformed, sessile coral exposed to oxybenzone for 8 hours. Source (although originally used from Source₁).

The study identified 62 parts per trillion of BP-3 as (arguably) the lowest concentration required to see any toxicity effect on corals. Worryingly, many popular coastal tourist areas far exceed this amount, for example 1.4 parts per million were detected in Trunk Bay of the Virgin Islands National Park.

Having read both the original paper and numerous related press articles, besides the significant dramatizing of language in media outlets (damage to juvenile corals became “fatal to baby coral” in this expressive Guardian article), I noticed that a lot of them failed to mention a key part of the experimental study – that different coral species responded differently to BP-3 exposure. In other words, each of the 7 tested coral species exhibited differing levels of tolerance. For this study, slower growing coral species were naturally more tolerant than faster growing species. In fact the species Porites astreoides was about 38 x more tolerant to DP-3 than the most sensitive species, suggesting that not all coral species are being “killed off” by sunscreen lotions - in fact some may be more tolerant than we’d expect.

Nevertheless, given the results of the study, I would still argue that reducing coral exposure to BP-3 is critical for sustaining the resilience of coral reefs, especially given the global coral bleaching event predicted with this year’s El Nino. Even with varying tolerance levels, exposure would still encourage a community shift to a less diverse and thus less resilient coral community. Furthermore, being a photo-toxicant, Oxybenzone's toxicity is exacerbated in strong light, making tropical regions where coral loss is already in a critical state even more vulnerable. With shocking figures such as at least 80% of all corals reefs already lost in the Caribbean, we really can’t afford to lose anymore from these places whose economies depend on tourist-income from coral reefs. Already, concerns in some areas have resulted in banning of products containing oxybenzone in managed marine areas. In Akumal Bay for example, the study site discussed in my previous post, visitors are encouraged to use either no sunscreen or sunscreen without BP-3. Furthermore, public relations campaigns such as “Protect Yourself, Protect the Reef!” have been set up specifically to reduce chemical contamination by suncreen-wearing swimmers in high-tourism areas.

Downs, the leader of the original paper’s research team, stated:

“Any small effort to reduce oxybenzone pollution could mean that a coral reef survives a long, hot summer, or that a degraded areas recovers. Everyone wants to build coral nurseries for reef restoration, but this will achieve little if the factors that originally killed off the reef remain or intensify in the environment.”

Downs makes two important points in this quote. Firstly, that coral reefs experience numerous stressors, both anthropogenic (e.g. trampling, climate change) and natural (ENSO events). Oxybenzone in your sun lotions may not seem like too big a problem, but it reduces the resilience of coral reefs to much more acute large-scale stressors, such as ENSO events that cause mass, global-scale coral bleaching events. Secondly, instead of trying to fix the problem through technical schemes (such as breeding “super corals” (!), perhaps we should firstly try and reduce our destruction of corals reefs in the first place.

So, in reply to the Daily Mail article’s questioning title ‘Is your sunscreen killing off coral reefs?’ we can turn to one of the aptly put answers of the avid commenter ‘BirdMail’: “Along with all the other crap we put in our oceans, yes, yes it is.”

One Guardian article states that oxybenzone is present in ~3500 brands of sunscreen worldwide, including Coopertone and L’Oreal. As conscious consumers, we should read the product labels and opt for coral reef-safe sunscreen, as well as wearing rash guards/scuba wetsuits rather than sunscreen.

Mallorca’s Water Management Strategies: A Critical Review

In order to reduce the extreme seasonality in tourist arrivals to Mallorca, and thus the huge impact on the island’s water resources in a short space of time discussed in the last post, Mallorca's local government have made strong efforts to adopt a "quality tourism model" in the hotel sector. This post aims to critically assess this management strategy, as well as alternatives.

The quality tourism model moves away from Mallorca’s typical mass tourism high rise high-density hotels that we all know and love, towards residential tourism in the form of large second homes. Aimed at wealthier tourists, this tourist accommodation is characterised by numerous water fixtures, particularly irrigated gardens, swimming pools and golf courses. The model takes an off-season strategy with higher open months annually, aimed at reducing seasonality.

This model has been strongly supported by Mallorca’s public administration since the mid-1990s, whose actions include reducing the need for environmental requirements in planning. For example, Law 6/2009 states that reports by hydrological planning sectors to ensure a good water supply are no longer required, in order to save administration processing time for planning and building residential tourist plots. Ultimately this amounts to a reduction in the government’s role in tourism planning - which doesn't bode well for the success of sustainable tourism.

Does It Really Work?

Since its implementation, there has been much scepticism regarding the quality tourism model’s effectiveness, in both effectively managing water resources and reducing seasonality of tourist water demand.

Per person, the quality model has greater water consumption than the mass tourism model. This is largely due to it's proliferation of garden irrigation, which accounts for >70% of quality tourist areas' summer water consumption. Furthermore, rather than reducing the strong seasonality in water demand, the high numbers of water fixtures (such as swimming pools) create a constant demand for water and additional annual peaks in water demand. This is exacerbated by the promotion of off-season tourism and greater open months annually which lead to peaks even in January which was previously the island's month of minimum water consumption. This acts to just increase Mallorca’s total water consumption, increasing it's vulnerability to potential climate change induced water shortages in the future.

Alternatives

Water supply can be increased through desalination, which in Mallorca accounted for 17% of the natural freshwater resources in 2014. Yet desalination has been critiqued as a “sustainability fix”. It has a very high energy demand, and it has been argued that the massive construction costs (e.g. 14,551,578 Euros for one plant in Palma, Mallorca) have contributed to Spanish state's financial crisis. Furthermore, the relatively high costs of desalinated water have lead to it's commodification and thus privatisation of public water supplies. For example, in Mallorca's Calvia municipality all water companies were publically owned until the 1990s, whereas now only one still is.

Overall, I would argue that rather than focus on technical fixes such as desalination, which come with their own environmental and economic problems, Mallorca should focus on more efficient management of the tourism sector's water demand. Although desalination can help increase water supply in the short-term solution, the root cause lies in reduction of water supply through strong seasonality in tourist arrivals and contamination of groundwater supplies, as discussed in my last post. Clearly, the quality tourism model acts to exacerbate the problem rather than solve it, therefore alternative strategies such as higher water efficiency standards in hotels and re-use of water should be considered. Furthermore, contamination of existing water supplies should be reduced through increased environmental accountability checks of hotels. The government should take a leading role rather than it's current reduction in involvement, as it has the power to both coordinate and implement the required policies and measures.

Trouble in Paradise Part 1: Tourism’s Contribution to Mallorca’s Water Crisis

Greetings curious readers! I trust you are well! Today’s post aims to explore the link between tourism and freshwater scarcity on an island I’m sure several of you will hold very dear to your hearts after last year’s field course – Mallorca! Mallorca is a particularly relevant case study regarding tourism and water use as it’s experiencing the freshwater shortages and problems many tourism-intense islands will probably have to face in the near future. The island has the highest water consumption in the Balearics (~82.5% of their total water consumption), yet it's water resource is scarce. This is the same for most small Mediterranean and Pacific Islands where, unfortunately, a big proportion of global tourism is concentrated. According to the Falkenmark Index, Mallorca’s freshwater availability lies well below the threshold of total water scarcity throughout the entire year, meaning that the island's demand for water surpasses the long-term sustainable yield of it's natural water resources. This in turn has resulted in unsustainable over-exploitation of the freshwater, particularly groundwater, especially from unregulated users.

So how has tourism contributed to this?

Tourism is the number one economic sector for Mallorca, accounting for about 48% (almost ½!) of the Balearic's GDP. Although tourism accounted for about 12% of the Balearic Island’s total water consumption in 2011, the sector's demand is rising much more rapidly than the biggest water consumer: agriculture. For example, the tourism sector's water consumption increased by a huge 156% in the Balearic Islands’ from 1980-95, as opposed to a 22% fall for agriculture.

Furthermore, the pressure on Mallorca’s water supplies from tourism is really concentrated in a short space of time. Both Mallorca's annual precipitation and peak in tourist arrivals exhibit a strong seasonality - the problematic part being that the two do not in any way coincide. The 4 driest summer months experience under 10% of the year's rainfall and really high evapotranspiration rates as well as over ½ of all tourist arrivals (as illustrated in Figure 1). Thus tourism acts to superimpose the island's yearly periods of highest water demand and lowest natural water availability.

Figure 1. Mallorca's annual tourist arrivals distribution for the years 2001-2009. Source.

Furthermore, the absence of long-term surface water resources on the island means groundwater is the main renewable freshwater, yet even this is unreliable due its dependence on the island’s highly variable precipitation. Even over a decade ago, researchers were highlighting the link between tourism and groundwater resource stress, pointing out that the most overexploited aquifers are usually located in tourist resorts.

Since then, the argument continues, with more recent papers arguing overextraction due to high summer tourist consumption has caused lowering of the groundwater table and water quality via saltwater intrusion. Other negative impacts of the tourist pressure on water quality include nitrate infiltration due to overuse of fertilisers and pesticides in maintaining hotel gardens and golf courses. Overall this results in a reduction in total available drinking water (and subsequent increase in extraction cost) for both the tourism sector and the local residents. In the future, this state of water scarcity combined with increasing occurrence of drought under climate change could lead to conflicts between different sectors and the local residents. For example, Bali, another tourism-intense water-scarce island, is currently facing a water crisis due to intense tourism development, with groundwater resources being reduced to critical levels, causing conflicts between local villagers who need water for farming and the tourist sector, which uses up a whopping 65% of the island’s water supply yet makes up 80% of the island’s economy. Although the tourism usage rate is much higher than for Mallorca, climate change will likely reduce the island's total water supplies, meaning it could be facing a similar situation soon.

Tune into the next post for an analysis of water management strategies being taken by the tourism sector in Mallorca to reduce this problem!

Sustainable Tourism: An Introduction

In the last couple of posts, we’ve been exploring the impacts tourism can have on the environment, both on a local and a global scale. These have not gone unnoticed, and in this blog post the responses to these damaging environmental impacts - most notably the idea of ‘sustainable tourism’ - are going to be introduced and explored.

What is Sustainable Tourism?

Sustainable tourism… ecotourism… responsible tourism…

You’ve probably come across loads of terms like these and more - and found that they’ve all blended into one big blur in your mind. So what do they all mean? How are they distinct from each other? Well, despair no longer my discombobulated reader, for herein lies all the answers…

The United Nations World Tourism Organisation (UNWTO, 2013: 17) defines sustainable tourism as “tourism that takes full account of its current and future economic, social and environmental impacts, addressing the needs of visitors, the industry, the environment and host communities.”

In other words, sustainable tourism is about applying the principles of sustainable development more generally to the tourism sector. In this sense, sustainable tourism isn't exactly a special form of tourism for a niche market, but instead a goal to make all types of tourism in all destinations more sustainable (UNEP, 2005). Given the dramatically increasing number of tourist arrivals in the late 20^th century, sustainable tourism isn’t understood as an alternative to mass tourism; well-managed mass tourism can and should be as sustainable as smaller-scale tourism (UNEP, 2005).

On the other hand, ecotourism and responsible tourism do refer explicitly to niche forms of tourism. Ecotourism, for example, specifically involves visiting relatively undisturbed natural areas whilst encouraging conservation and environmental awareness, usually in small groups (UNEP, 2005).

I'm not sure the elephants' idea of 'getting close to nature' was what the ecotourists had in mind... (Source)

What does Sustainable Tourism Involve?

Regarding the environment, sustainable tourism aims to “make optimal use of environmental resources that constitute a key element in tourism development, maintaining essential ecological processes and helping to conserve natural resources and biodiversity” (UNWTO, 2013: 17).

Right, well that’s all well and good, but in reality achieving this goal is pretty difficult and complex.

Let’s go back to the first definition of sustainable tourism – “addressing the needs of visitors, the industry, the environment and host communities” (UNWTO, 2013: 17). As this quote exemplifies, many different stakeholders engage with the tourism sector, or influenced by it. All these groups have different interests and levels of influence on the industry. Yet a critical requirement in sustainable tourism's success is for stakeholders to collaborate effectively in management of the sector, making their roles and relationships in the implementation of sustainable tourism very important. This requires organised coordination and partnerships, both at the local and national destination levels (UNWTO, 2013) - often easier said than done. Figure 1 gives an overview of just a small number of the stakeholders involved in the industry and what their roles could be in achieving sustainable tourism.

Figure 1. Different stakeholders in the tourist industry and their suggested roles in delivering sustainable tourism. Adapted from UNWTO, 2013.

Alright – so we’ve gone over the need for stakeholder coordination in achieving sustainable tourism – so what actually needs to be done? What actions can go about making “optimal use of environmental resources” and “maintaining essential ecological processes”? (UNWTO, 2013). Well, there isn’t really a straightforward answer to this…

The UN World Tourism Organisation identifies measures like planning controls, financial incentives and certification as ways to promote sustainable tourism in a destination (UNWTO, 2013). But do these actually work? Buckley (2012) argues that so far, attempts made by the private sector to achieve sustainability, such as self-regulation and ecocertification have been pretty much ineffectual. This is for a number of reasons. Private companies often opt for environmental self-regulation in order to avoid stricter external government regulation (Núñez, 2007). In this way, they can carry on with environmentally unsustainable practices under the guise of sustainable tourism (Buckley, 2012). Furthermore, Mair and Jago (2010) argue few tourists themselves choose between services specifically based on their sustainability; instead they generally expect good environmental practice to be incorporated into services as routine. As an avid traveller I’d say I have to agree – I can't say I've ever chosen a particular airline or hotel purely based on its environmental performance.

Instead, it has been suggested that environmental policies, management measures and technologies have greater potential to reduce the environmental impacts of tourism (Buckley, 2009; UNEP, 2011). For example, advances in energy efficiency can help reduce waste generation and resource consumption locally (Buckley, 2012). Furthermore, although most environmental damage linked to tourism is caused by private companies and tourists, governments should take a leading role in achieving sustainable tourism (UNEP,2005; Buckley, 2012). Strong leadership is needed because the tourism sector is really fragmented and coordination between stakeholders for an effective sustainable tourism strategy. Governments have the necessary authority to implement strict environmental regulation and economic incentives on private businesses, which Buckley (2012) argues is the main driver for improvement. For example, improved sustainability in hotels can be driven by measures such as local government regulation for planning, external impact assessment and pollution control (Buckley, 2012). Similarly, NGOS have an important role in coordination and getting the voices of less powerful stakeholders heard – such as the local community, smaller businesses and tour operators (UNWTO, 2013).

The Future...

Lastly, the need for quantitative and widely applicable sustainability indicators for the tourist sector has long been recognised. This article in the Guardian from a couple of years ago argues it is the role of local governments and authorities to collect this globally comparable quantitative information on the environmental impacts of tourism in particular destinations. It is this lack of precise information on destinations which hinder the development of direct targets.

Regardless of who is responsible for collecting the data, coming up with the indicators is a difficult task – how would you define a sustainability indicator? What would you include in it? Nevertheless, establishing quantitative and comparable environmental performance measures should be a key priority for sustainable tourism research (Buckley, 2012).

Tourism and Coral Reefs: What's the Damage?

Tropical coral reefs cover less than 1% of the ocean, yet rival only rainforests as the most diverse ecosystems on Earth, providing vital services such as home and nursery to a quarter of all marine fish species. They are of utmost importance to humans and our economy, with 500 million people dependent on them for livelihoods. Healthy coral reefs are especially important for local tourism, through providing appeal for diving tours and fishing trips; furthermore, businesses based near reef systems such as hotels provide millions of jobs and income globally (Figure 1). Yet the latest global coral reef assessment states an estimated 19% of coral reefs are now dead and lost, and the tourism industry is far from guilt-free.

Figure 1. The breakdown of component values that contribute to the global annual economic value of coral ecosystems. Source.

Over these last three decades (e.g. 1990s, 2000s, and 2010s much of the research on tourism’s impact on coral reefs has centred on recreational activities, particularly snorkelling and scuba diving.

For example, a recent paper (Gil et al., 2015) based in Akumal Bay in Mexico, found that increasing snorkeller numbers generally have a significantly negative impact on coral cover. Coral reefs' structure and functioning centres on the balance between corals and algae, with which corals have to compete for benthic substrate.

A survey of the bay’s benthic community in 2013 compared sites in a snorkeller-intense zone with those at a proximate control zone featuring 13 times lower tourist numbers (Figure 2). The results show lower coral cover across all coral morphologies in the high-tourism zone, (although this effect was only significant for plating coral cover). Furthermore, tourism-intense sites featured significantly increased dead coral cover (a 50.5% increase from control to tourism sites; p < 0.05), and a greater abundance and number of taxa of benthic algae, although this was not significant.

Figure 2. May 2013 Mean (+/- 95% confidence intervals) percentage cover of corals and numbers of algal taxa/fishes, from the control zones (light bars) and the tourism-intense zones (darker bars). Source.

The study focuses on the increasing number of snorkellers as the causative variable for reductions in coral cover in the high-tourism zones. I agree that the presence of snorkellers and SCUBA-based reef tourism can drive coral reef degradation. Indeed, similar results are found in a number of different studies throughout the years. You can imagine why – to describe just a couple of mechanisms: direct, physical contact of snorkellers with corals (trampling, touching) can easily degrade coral skeleton and tissue, and snorkellers can cause localised water column sediment re-suspension, reducing recruitment and survival of corals through choking them. *

However, Gil et al.’s (2015) use of variables such as ‘no. of tourists in water’ and ‘number of snorkellers’ effectively lumps together all activities associated with snorkelling – from the individual snorkellers to the dive boats and anchors and their associated impacts. Because of this, I was sceptical as to whether the reductions in coral cover in the high-tourism zone (Figure 2) were really down to individual snorkellers, or whether there could be other tourism-related activities associated with the increasing numbers of snorkellers driving that difference, which was encapsulated within their metric of ‘number of snorkellers’, but not quite specified.

A bit of digging later, I found an excellent (albeit slightly dated!) study quantifying the degree to which separate tourism activities individually impact on coral reefs. Two of these impacts - dropping anchors and their chains on reefs and physical diver contact – both could have been encapsulated in Gil et al.,’s (2015) variables ‘no. of tourists in water’ and ‘number of snorkellers’ and thus driven the reductions in coral in the high tourism zone (as an increasing number of snorkellers could also entail an increasing number of dive boats dropping anchor). The results of this study took me by surprise; given the volume of research on the impacts of snorkelling and SCUBA diving on coral reefs, I assumed the greatest impact on coral cover would be from physical diver contact. However, anchors and their chains (from dive boats) had a whopping mean coral cover damage of 7.11% in contrast to a very moderate diver contact mean of 0.67%. Dropped anchors can break live portions of a coral colony into fragments, gouging out large chunks of coral skeleton and tissue – which often die and turn into rubble clouds, choking the surrounding corals. In contrast, the model results indicate that SCUBA divers and snorkelers tend to damage coral reefs on a smaller, individual scale. This would suggest that perhaps ‘number of snorkelers’ is a slightly simplistic metric when advising management, as it largely overlooks the difference in impact between separate activities associated with rising snorkeler numbers. A manager reading Gil et al.’s (2015) paper may focus on educating snorkelers on coral damage – when in fact they should be focusing on initiatives such as designated mooring lanes for dive boats to reduce coral damage!

Furthermore, the focus on snorkelling and SCUBA diving in the wider field of tourism-related coral disturbance research fails to appreciate the more indirect impacts of coastal tourism development on reefs. Such development increases land-based runoff events that drive nutrient enrichment (a global problem which can occur for example where hotel sewage is allowed to enter the coastal system) and sedimentation, promoting benthic algal domination over corals. Indeed, the National Oceanic and Atmospheric Administrations (NOAA)’s ranking of major threats to coral reefs ecosystems by region shows that coastal development and runoff poses a high priority threat in 10/14 regions of the world, as opposed to only 1/14 for tourism and recreation (Figure 3).

Figure 3. Ranking of major threats to coral reef ecosystems by region. Source.

A recent experimental study based on coral reefs in the Gulf of Panama showed that coral loss and algal growth induced by overfishing was magnified and accelerated when sediment addition or nutrient enrichment was combined with overfishing (Figure 4). It has been argued that overfishing is the fundamental factor driving community shifts to algal-dominated tropical coral reefs. This indicates that coastal tourism development can play a major role in coral reef degradation through exacerbating the pressures already being placed on coral reefs, such as overfishing.

Figure 4. Change in benthic composition over the experimental period. Changes in percent cover from initial values displayed in separate panels for different community members. Lines, styles and colours indicate the effects of different combinations of stressors: overfishing = dashed lines; sediment addition = yellow lines; nutrient enrichment = blue lines; both nutrient enrichment and sediment addition = green lines. Source.

An overall point of this post is that the localised impacts of tourism on coral reefs often co-occur, and damage cannot be attributed to divers alone. A final take-home point is that these local impacts are always experienced in the presence of global anthropogenic stressors, such as increased sea surface temperatures and ocean acidification, and regional-scale natural disturbances to coral reefs such as the El Nino-Southern Oscillation or hurricanes, which could also see shifts in their regimes in the near future due to climate change. In fact, this year’s El Nino event may even outdo the peak event of 1997-98, meaning that coral die-off in 2016 could be particularly severe as the bleaching event causes them to lose their algal coating. The tourism industry itself is increasingly contributing to these global pressures, for example through releases of greenhouse gases associated with increasing air travel (see my previous post!). This is important because the background effects of climate change are expected to generally reduce ecosystem resilience, increasing the impact of tourism’s local stressors.

This online photo gallery dramatically illustrates some of the horrific effects of human impacts on coral reefs discussed in this blog post.

*For more info on the direct impacts of snorkelers and SCUBA divers on coral reefs – check out this blog!

Invasive Species: Global Hitchhikers of Tourist Flows

Greetings to all the wonderful, magnificent curious readers out there!

Tourism often involves gatherings of multiple flows of individuals, vehicles and sea vessels from geographically wide-ranging parts of the world, providing a source of non-native (and potentially invasive) propagules including seeds and spores. Thus tourism creates key paths for transport of non-native species, a problem projected to increase in importance with further expansion of the sector.

This blog post was largely sparked off by a study hot off the press. It represents the first global meta-analysis of the link between tourism activities and the arrival of non-native species.

The results of the study show that globally non-native species are more abundant in areas featuring intensive tourism activity, with an overall significant large positive effect size (0.879, p>0.001) in sites where tourist-related recreation activities occurred. Although both land- and aquatic-based recreation activities pose a significant and large influence on non-native species abundance (Figure 1), their abundance is higher in aquatic environments, with boats having a greater effect than the other two vectors (horses and visitors/trails). 

Figure 1. Meta-analysis forest plot (+confidence intervals) displaying the mean effect size of overall and different recreational tourist activities on abundance of non-native species. Effect size values greater than 0 indicate non-native species abundance was greater at sites featuring recreational tourist activity occurred than in the controls. Confidence limits overlapping the dashed line are not significant. Source.

Across the meta-analysis the abundance of several types of aquatic non-native species, from seaweeds to bryozoans, was significantly greater in sites where tourism-related boating and yachting took place than control sites. Similar to national parks, marine reserves attract high tourist visitation rates and tourism-related recreational activities. This leads to the concentration of potential invasive species transport vectors such as diving equipment, boat ballasts and anchors and fouled hulls. Thus despite the terrestrial focus of the majority of studies on invasive species and tourism, recreational boating/angling is believed responsible for over 1/3 of non-natives pathways into Europe. For example the zebra mussel’s  spread into Ireland has been attributed particularly to vessels that are not regularly maintained and berthed for long periods, such as private cruisers used for tourism.

Nature-based Tourism and Invasive Species

Whilst tourism may not be the main way invasive species are spread (with shipping and industry being the two major pathways, it is one of the only pathways capable of introducing them to extremely remote parts of the world. Nature-based tourism (involving outdoor recreation and wildlife viewing) and new forms of “extreme/adventure tourism” are key growth areas in the sector. These are commonly based in comparatively pristine and high biodiversity sites such as national parks, and often in developing countries. Therefore as such forms of tourism continue to increase in popularity, an associated increase in the tourism-assisted passage of non-native species to these remote locations could have catastrophic consequences to local biodiversity. Flora and fauna residing in these habitats are often endemic and have evolved in isolation, and as such are likely to be less resilient to new pressures such as non-natives and any associated pathogens.

Aconcagua Provincial Park in Argentina is a protected area on a mountain region that experiences high levels of endemism, providing essential ecosystem services to the lowlands. It is a popular tourist destination amongst European hikers, and in the last 2 decades visitation has increased at approximately 10% annually, with > 6000 visiting hikers in 2011. A recent study recorded at least 21 non-native plant species in the Aconcagua region, with 16 of these only recorded within the park between 2001-2011, in tandem with increasing visitor numbers. All species were native to Europe and 8 are considered international invasive environmental weeds. Due to the very limited vehicle access and previous human use and isolated nature of the park, it is probable that tourists were the main vectors of non-native seed dispersal. Such propagules were likely carried in on their clothes, shoes and personal mountaineering equipment (which they may have previously used outside South America), and in the dung and fur of pack animals which can create microhabitats favourable for establishment of invasives in harsh environments. Furthermore, the dominance of European non-native species could reflect the increasing tourist flows from developed countries to remote natural habitats in developing countries through increased popularity in nature-based tourism.

Non-native plants were recorded more frequently in disturbed vegetation (52%) than in natural vegetation (38%), particularly those areas heavily trampled by hikers and pack animals. Popular recreational activities including hiking, off-road driving and mountain biking can cause habitat disturbance acting to destroy the flora and fauna of a site, changing species' niche dynamics and opportunities.  Non-native species often have particular success in disturbed areas as features such as their faster growth and reproduction rates allow them to rapidly colonise disturbed habitats. In this case, trampling on and off trails by tourists and pack animals favoured non-native establishment through reductions in native vegetation cover and increased soil erosion. Figure 2 shows how the occurrence of non-native species is concentrated along the main hiking pathways for mountaineers, where the maximum disturbance occurs.

Figure 2. Location of sites surveyed for the intensively used trails of the Horcones Valley in Aconcagua Provincial Park, Angentina. Sites with non-native species (black cirlces) and only native speces (white circles) are shown. Source.

Similarly, a study in 2014 found that survival of the invasive non-native species Poa annua was 33% higher on Antarctic sites with disturbed soils. P. annua competed with the native plant species for resources and space, having significantly negative effects on their photosynthetic performance and biomass. The authors suggest that disturbed soils contain higher levels of nutrients, so that like the mule dung in Aconcagua, human disturbance through tourism may generate microhabitats more favourable to the non-native species. This example is particularly worrying as Antarctica’s severe environmental conditions and isolation meant researchers thought it was pretty much immune to invasives. But – where there’s a will, there’s a way – and tourism has found that way! The non-native species recorded in Antarctica, such as Poa annua – are mainly found near scientific bases and tourism cruise landing areas. During the 21^st century, Antarctic visitor numbers have increased dramatically, mainly due to tourism, and now roughly 40,000 people - mostly tourists - visit each year. All the clothes, luggage and scientific equipment of Antarctic visitors may carry non-native seeds/spores, and an article in the National Geographic stated that, worryingly, on average tourists to Antarctica in 2007 each carried 2-3 seeds, and that 49-61% of these foreign plant materials were cold-adapted species. The limited species richness and simple community structures make Antarctica's ecosystems especially vulnerable to changes in plant communities occurring with non-native species establishment.

Of course the role of tourism in facilitating non-native species access to remote locations is not restricted to terrestrial environments. Whilst not necessarily linked to nature-based forms of tourism, long-distance yachting is potentially one of the very few transport vectors able to introduce non-native species to marine environments around highly remote ocean islands: ecosystems for which non-native introductions are believed to be the primary threat for biodiversity loss. For example, Palmyra Atoll, a remote island in the Pacific, holds one of the very last near-pristine reef ecosystems remaining globally. However in 2011, a study recorded 5 non-native invertebrate and algal introductions. Leisure-related yachts arriving from harbours like Hawaii, where all 5 of these species have been recorded as non-native, are the most probable source. In particular, the red alga Acanthophora spicifera was most likely transferred to Palmyra through small vessels’ hull fouling, as private yachts can enter Palmyra’s lagoons without standard checks for invasive hitchhikers. This and other algal invaders pose an ecological problem as they have the potential to alter the coralline algal dominated reef terrace environments.

Some Last Thoughts

The map below shows the location of the 32 studies included in Anderson et al.’s (2015) global meta-analysis. As you can see, a lot of them seem to be concentrated in North America, Europe and Australia. Furthermore, the number of studies included for calculating the effect size tourist activities in marine environments (n=8) was less than terrestrial environments (n=11) (Figure 1).

Map showing location of the 32 studies of invasive species included in Anderson et al.'s (2015) global analysis. Green dots = land; blue dots = marine and freshwater habitats. Source. 

In the above discussion, I hoped to rectify this bias somewhat towards developed countries and terrestrial environments in Anderson et al.’s (2015) study which highlights a wider problem of bias in the research field of tourism-related transport of non-native species. The examples I’ve drawn upon ultimately show that even isolated, high-elevation specifically protected areas, the coldest and driest places on Earth, and islands pretty much in the middle of nowhere, are susceptible to plant invasions, specifically via tourism.

Love this post but want more on those pesky little hitchhikers? Totally understandable. Check out my friend Ben’s blog, especially this post for a great insight into the impact invasives have on ecosystems!