Over the past four decades, there has been much research on the negative environmental effects of tourism. The UNWTO reports that tourism grew 5% in 2018 to reach 1.4 billion total international tourist arrivals with tourism exports amounting to USD 1.7 trillion . Tourism and its associated activities have become the bread and butter of many developing nations, especially the small remote islands that lack resources to engage in socio-economic development. As the concept of eco-tourism has gained ground around the world, more and more people travel to experience nature-based activities that are directly or indirectly related to the environment. Thus, the number of tourists travelling to Asia to experience unique hiking trails or to islands like Aruba to take part in undersea expeditions has considerably increased. Yet, with so many people travelling, it is inevitable that negative environmental effects will not arise.
One of the most menacing negative impacts of tourism on the environment is indisputably biodiversity perturbation. Many studies have shown that tourism can have drastic consequences on biodiversity if not properly managed . The Secretariat of the Convention on Biological Diversity declares that the major reasons for biodiversity decline (including pollution, overexploitation, habitat change, climate change and the introduction of invasive species) are all closely linked to the tourism sector . While extinction is a natural process, tourism related activities are increasing the rate of this phenomenon. In China, for example, the construction of tourism facilities in the Changbai Mountain Reserve decreased considerably the tundra cover in the surroundings while the Bitahai Wetland Scenic Area reported large losses of vegetation because of trampling, plant picking, invasion of alien species, horse manure disposal and horse grazing .
Moreover, tourism can cause disturbance on wildlife with regards to their behavior especially during nesting and breeding seasons. Research on animal behavior in the presence of tourists reveals that animals can experience immediate changes in behavior, depart from their native regions, decrease in numbers/distribution (which can then affect overall species compositions and interactions) and result in changes in physical strength, health and sexual capacities . Such behavioral changes have been noted in elephants, kangaroos, gorillas, whales, wild horses amongst others and more often than not, certain bird species have not even returned to their homelands.
Sadly, today, many tour operators and agencies are capitalizing on endangered species. For instance, Antarctica tourism has become famous in the last years by pitching polar bears as ‘must-see before they disappear’. Such advertising campaigns are increasing for many species as climate change manifests itself with the threat of species loss in the coming decades. As people rush to see these exotic animals and plants to form part of the ‘ones who saw’, they also exert a lot of pressure on them not only by pollution and the like but behaviorally also by instigating stress which may affect their reproductive success.
The aquatic environment is an important element of the tourism sector. It is estimated that direct water consumption per tourist can be roughly 84 to 2,000 l/per day  which can cause some tourist destinations to become water-stressed. Tourism activities can cause water pollution in the form of sewage discharge consequently leading to eutrophication, loss of biodiversity and collapse of aquatic ecosystems. Also, as polluted water infiltrates underground, it can contaminate aquifers; decreased water quality has been noted in many countries such as China, India, Sri Lanka and Australia due to tourism-related activities. Littering as a consequence of tourism is also common thereby decreasing the aesthetic values of sites and poisoning wildlife. Famous tourist destinations like Thailand and the Philippines had to suspend access to certain tourist spots to clean up dumped sewage and allow the sites to recover from pollution.
With 80% of all tourism occurring in the coastal regions, the damaging impacts of tourists are even worse. This is seen in, firstly, the massive clearance of mangrove forests and seagrass beds (which naturally clean up polluted water from the land and prevent damage to ecosystems upstream such as coral reefs) and secondly, in the amount of waste that is produced and dumped into the sea. Many nesting sites for marine creatures such as fish, turtles and marine mammals have been lost and many more have been killed due to rubbish ingestion or trapped in them. Similarly, careless recreational activities like snorkelling, boating and diving can damage coral reef directly or indirectly when anchors hit the ocean bottom and stir up sediment that chokes coral polyps. As the number of cruise ships, resorts and floating towns also rises, the amount of untreated waste discharged directly into the ocean also increases.
Moreover, tourism has a severe impact on air quality. As an example, air pollution in the Changbai Mountain National Nature Reserve in China was linked to tourists’ use of fossil fuels for cooking and heating . In general, the majority of tourism-related activities from aviation to shopping depend on fossil fuels. A recent study on carbon emissions from 160 tourist destinations declares that the amount of carbon released by the tourism sector has increased by 4 times (3.9 to 4.5 Gt CO2e during 2009 to 2013) than previously estimated . Carbon emissions account for 8% of all total greenhouse gas emissions and come mostly from tourism-related transport, shopping and food.
To add to this, changes in air quality in caves have also been noted as a result of increasing tourist visits. In France, the Lascaux Cave paintings got tarnished by an abundant growth of algae in the cave mainly due to the extra use of artificial lights and increasing levels of carbon dioxide released by tourists [7,8]. Similarly, cultural tourism also influences air quality. When incense, coal and timber are burnt in large amounts for worship, noxious gases such as sulphur dioxide are released into the air as has been observed in many countries like India, China and Taiwan.
Another negative impact of tourism on the environment is through noise. Where people gather for fun and activities, the soundscape is inevitably affected. Noise results due to traffic, development, movement and behavior amongst others. Generally, a sound level beyond 50 dB is regarded as noise in any tourism area . In the natural environment, loudness can have significant impacts on wildlife leading to hostility or fear. Thus, while some animals may completely avoid certain areas due to noise, others may have problems to mate and nest. What’s more, birds and frogs may even have to change their call frequencies to be heard .
Unplanned or irresponsible tourism development can seriously affect the quality of the land leading to hazards such as soil erosion, landslides, avalanches and desertification. In the same manner, tourists themselves greatly change the soil composition along their journeys as reflected in Nepal whereby forest trekking led to a loss in soil fertility and erosion . Indeed, several studies confirm that trampling in nature reserves significantly changes the soil quality, sometimes preventing certain plant species to grow while land pollution alters the physicochemical properties of the soil such as pH, porosity and compaction abilities.
While all these points examine tourism’s negative impacts on the environment, it is also worth to note that these actions are not always deliberate. As it is, one of the major issues associated with environmental impacts is about deliberate and accidental impacts. Deliberate impacts are more commonly obvious especially from consumption activities like fishing and hunting but accidental impacts are more difficult to monitor . Most agencies involved in those intentional impacts on the environment must often be subject to specific legislation, permits, constraints and obligations while poaching is categorically illegal. Yet, environmental change takes a long time to materialize and in many cases, tourists may be unaware of their impacts on the surroundings even though they may visit the same place very often. What’s more, these impacts are often cumulative in nature such that individual impacts may be insignificant but could have noticeable effects over time such as cliff climbing or mountain climbing with heavy gear.
In the end, it must be understood that there is a complex relationship between tourism and the environment: claiming that any specific type of tourism will not be environmentally damaging is naïve and pretending that all forms of tourism are environmentally damaging is unrealistic both economically and environmentally . Thus, to maintain the equilibrium between environmental preservation and socio-economic progress, sustainable tourism should be embraced.