"Ecotourism has two sides to it nowadays," says Jonas De Schrijver, a Southeast Asia ecotourism consultant. "The real deal, or just a label. A while ago ecology was an ideology. Now, in many cases, it's a business."

In Southeast Asia, sustainable tourism tends to be a lot less structured than in the rest of the world and "planning is a little tricky", says Lefevre, founder of Kimshi, a mobile marketplace for niche tourism in the region.

"Plan your tours with conservation and the environment in mind," says C.W. Cheung, head of WWF Hong Kong's Footprint Programme. Seek out tours that support conservation work, by offering financial donations or the chance to help out at worthy projects.

Simple measures can create big changes. Small steps include eating local produce, not having towels washed daily and saving water when showering. "Try setting your phone alarm and challenge yourself to come out in less than five minutes," Lefevre says, adding that showers use between 12 and 40 litres of water per minute.

Ways to reduce waste include not littering, replacing plastic bags and wrappings with reusable boxes. You can offset your carbon footprint by taking in the landscapes by bicycle or on foot. What's more, you can stop off and talk to the locals along the way.

"At the individual level, small changes might not sound like much but multiply this by one billion travellers and then change will come to our planet," Lefevre adds. "Eco-consciousness is a global movement, and this is just the beginning."

Responsible travel is also about the people living in the lands being visited. There are plenty of ways to see the sights while giving a helping hand.

Friends International, an NGO that works with underprivileged children in developing countries including Cambodia, Laos, the Philippines and Myanmar, urges tourists not to fall for the charm of street kids by buying handicrafts, books, scarves or other trinkets. This, it claims, fuels the long-term cycle of poverty by keeping children out of education.

The NGO also spearheads a Children Are Not Tourist Attractions campaign, appealing to tourists not to visit orphanages or schools in exchange for money or engaging in "voluntourism" trips. Instead, it says that the best way to support vulnerable children is to help keep families and communities together by supporting community-based projects and initiatives that make a difference.

Staying in local guesthouses and home-stays can enhance the experience while directly injecting cash into underprivileged communities.

De Schrijver heads Sustainable Adventures in Cambodia, which operates group tours into the rainforest that covers the pristine Cardamom Mountains. Adventurers get to stay with villagers.

This sees local communities host guests in their homes and can give them jobs as tour guides, which brings in a sustainable income. It also provides a platform to educate the local population on the importance of preserving their surroundings.

"We have turned hunters and loggers into guides and taught them about the importance of preservation," he says. "Ecotourism should always be community-based because indigenous communities in these areas are just as much part of the local ecosystem as the trees or the birds."

When booking accommodation, several green certifications exist, including Green Seal and Green Key Global. It's worth checking out eco-friendly initiatives recognised by internationally recognised schemes, such as the World Responsible Tourism Awards.

However, with eco-accreditation lacking in the region, asking questions about water and waste recycling policies, attempts to offset carbon emission and any local projects they support, should give a good indicator of the validity of their principles.