We should seriously plan against overtourism. There can be too much of a good thing.

OPINION: In a world of easy and affordable travel, it is easy to become strangers in your own city, while tourists stay in Airbnb of Ikea-catalogue charm, and sit in "authentic" local establishments watching other tourists. In the world of tourism, overtourism is the buzzword and we need a plan.

Global tourism has grown exponentially over recent decades. The cost of travel has come down. It's easy to research and organise a weekend away with a few clicks, and more people have the income to travel.

We shouldn't expect global tourism to slow. Travel is becoming cheaper and easier. In our selfie world of cheap consumer goods, travel offers a great way to break the boredom of daily life.

In New Zealand, we now get nearly 4 million visitors a year, up four-fold since 1990. Kiwis took nearly 4 million trips offshore, also up four-fold since 1990. Sometimes it's cheaper to go on a overseas trip than a local holiday.

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For a long time tourism policy has been about luring more people in. Often with little thought of what it means for the hosts.

Yet, hospitality can be exhausted. In Palma locals threw horse poo on tourists. Police stand guard at the Trevi Fountain. In Paris, Airbnb is strictly regulated. In Venice, activists have stopped cruise ships from entering the harbour. In Barcelona, "tourists go home" is graffitied on walls.

Tourists don't want the same things as locals. Airbnb prices are much higher than the same place rented to a local. The local pub or cafe will serve tourist-friendly fare at tourist prices, often crowding out locals. Workers in the industry can no longer afford to live where they work.

123RF Beaches aren't so pristine when there are hundreds of tourists there.

Tourists don't need a hardware store, or a shoe repair shop. When tourism takes over, the makeup of a local community changes rapidly.

Beyond a certain point, tourists metamorphose from an economic-life-giving force, to an economic and social predator, changing and swallowing up the very things that attracted them initially. Locals seemingly become an extra at a theme park.

We also need to be mindful of the benefits, which are not spread far and wide. Airlines, hotels, transport and hospitality operators benefit, but many of the local jobs tend to be seasonal, insecure and low-paid.

The alternative may be no job, so tourism shouldn't be scorned. But you cannot build a resilient and successful economy on tourism alone. Places too exposed to tourism are also at the mercy of changing tourism patterns.

LAWRENCE SMITH/STUFF Shamubeel Eaqub: "For a long time tourism policy has been about luring more people in. Often with little thought of what it means for the hosts."

The costs and benefits of tourism are shared unequally across local communities and central government. The stresses on the community infrastructure are borne by locals, but majority of the spoils go to central government in tax revenue from sales, wages and profits.

Unless tourism can grow alongside looking after the host community, including affordable housing and maintaining the authenticity and social fabric of a location, it becomes overtourism.

What we sell to tourists is perishable. The silence on the mountaintop or the expansiveness of a pristine beach are gone when hordes invade. There is good reason to think about an optimal level of tourism and for using tools like limiting flight numbers, taxes on accommodation, responsive housing supply and redistribution of tax revenue to tourism-intensive regions.

Often one place may become over-touristed, but its neighbour is under-done. It's difficult to spread the hordes. They'd rather have the same Instagram post than something different. Many places are trying, but with limited success.

Fundamentally overtourism represents a frequent economic problem. The externalities or costs to the community and environment are not fully accounted for, or compensated.

Tourism is our biggest export and too big to be complacent. We should seriously plan against overtourism. There can be too much of a good thing.