Whilst big companies (cough *Shell, BP* cough) and governments do shoulder most of the responsibility for our planet’s deteriorating state, there are small changes that we can make to help alleviate the massive carbon footprint that travelling can leave.
The first, biggest one (and perhaps the hardest to execute) is to avoid flying, or, if you do fly, pay that small extra to off-set the carbon emissions. Unfortunately, it is out of the average tourist’s ability to invent a way to fly that doesn’t use a big amount of fuel, but there are ways to avoid it until someone gets their mind in gear to invent it. For Europe, consider trains or inter-railing - a gap year staple. Slow travel is also becoming more popular, and is much better for the environment. After all, the journey is just as important as the destination.
In terms of accommodation, look for places that advertise sustainability, or alternatively look for house-sitting or dog-sitting as an alternative to using Airbnb. This could also be a way to save money without feeding into the current issue of Airbnb-fuelled gentrification of many areas such as Barcelona.
Another great way to support the local culture is to shop at independent businesses. This is also better in terms of the environment, as more often than not their products will be locally sourced instead of imported. Alongside this, it's also very important that, when holiday purchases are made, they are made with longevity in mind. They're for life, not just for the holiday - or at least to make the trip home instead of ending up in a poolside bin.
These small changes, among others, can make all the difference - and a little change, on a personal scale, is better than none if we are going to keep these travel destinations alive and kicking.