Formal pairs suit Writing Task 2. Neutral ones work anywhere. Informal ones belong in Speaking.
1.mass tourism
formaltravel by very large numbers of people to the same places
Mass tourism has damaged some of Europe's most beautiful coastlines.
Usually used critically.
2.a popular tourist destination
neutrala place that many tourists visit
Bali has become a popular tourist destination for Australians.
Holiday destination is a close alternative.
3.boost the local economy
neutralmake local businesses earn more money
Festivals boost the local economy by filling hotels and restaurants.
Benefit and support also collocate with economy.
4.sustainable tourism
formaltourism that limits harm to the environment and local people
Sustainable tourism means fewer visitors who stay longer and spend more.
Ecotourism focuses on nature in particular.
5.preserve cultural heritage
formalprotect a place's traditions, buildings and history
Ticket income can help to preserve cultural heritage sites.
Protect is a simpler alternative.
6.historical sites
neutralplaces of historical importance
Visitors should not be allowed to climb on historical sites.
Heritage sites is the formal term.
7.a package holiday
neutrala holiday where travel and hotel are sold together
A package holiday is the cheapest option for many families.
British. Book a package holiday.
8.go sightseeing
informalvisit famous places as a tourist
We went sightseeing in Rome for three days.
Do some sightseeing is also correct.
Avoid: go to sightseeing → go sightseeing
9.travel abroad
neutralgo to another country
More young people travel abroad before they start university.
Abroad is an adverb, so no to before it.
Avoid: travel to abroad → travel abroad
10.peak season
neutralthe busiest time of year for tourism
Hotel prices can double in peak season.
Off-season and low season are the contrasts.
11.the tourism industry
neutralall the businesses that serve tourists
The tourism industry employs one in ten workers in some countries.
The tourism sector is a formal alternative.
12.off the beaten track
informalfar from the places most tourists visit
I prefer villages off the beaten track to famous cities.
An idiom for Speaking; avoid in Writing Task 2.
13.a tourist trap
informala place that charges high prices to tourists for poor value
The restaurant near the cathedral is a bit of a tourist trap.
Speaking only.
14.a strain on local resources
formalheavy demand on water, roads and services in a place
Millions of summer visitors put a strain on local resources such as water.
Place or put a strain on.
15.seasonal employment
formaljobs available only at certain times of the year
Tourism often offers only seasonal employment, leaving workers without income in winter.
Seasonal work is the more neutral version.