There are 2 different contributions on this topic.
Green transition of tourism companies :
We commit to operating our business sustainably and building a culture of sustainability. 
We are leading by example by setting carbon reduction targets in line with climate science guidance and by empowering our people to make sustainable choices in their day-to-day work. Using 2019 as a baseline, we have used the Science-Based Targets Initiative (SBTi) criteria for a 1.5C future to develop short and medium-term reduction targets.
Measurable targets:
- 95% reduction in scope 1* & 2** emissions by the end of 2030 from 2019 baseline 
- 50% reduction in scope 3*** emissions by the end of 2030 from 2019 baseline 
- Achieve net-zero by 2040

*Scope 1 emissions are natural gas used in offices, fuel for leased company vehicles
**Scope 2 emissions are electricity from offices and data centers
***Scope 3 emissions are purchased goods/services, business travel, employee commuting

Green Transition of tourism SMEs:
We are committed to making it easier for travellers to book more sustainable trips. Supporting tourism accommodations in developing their sustainability programmes, while recognising those who have already made significant efforts to improve the sustainability of their operations. By showcasing these efforts on our platform (increasing the supply of more sustainable travel options), we aim to make it easy for travellers to book more sustainable travel. Today only a small number of tourism accommodations have invested in existing sustainability certifications.

We have launched the Travel Sustainable Programme that has 2 central components: 
1) Educating and raising awareness amongst tourism accommodations on their impact in the environment they operate in. Initially 32 sustainability practices have been independently validated as impactful. We have been working with the Global Sustainable Tourism Council, Travalyst, Sustainalize and other sustainability experts to share what properties can do to make positive change in the industry. Through the Booking.com Sustainability Handbook, available in 30 languages, Booking.com supports partners to understand which practices may make more sense to them, what impact they will have; sharing tips and best practices. The objective is to get accommodations started on sustainability.
2) A badge and filter on our product. The badge is awarded automatically to accommodations who already have one of 37 3rd party certifications we accept as part of our framework. For those properties that have implemented sustainability programmes or adopted sustainability practices but cannot afford or commit to the requirements of a 3rd party certification, our programme will award a badge if they reach a sustainability impact threshold, assigned per continent and independently validated as part of our framework. Travel Sustainable is an evolving programme, designed to make sure that no accommodation however small, is left behind in the sustainability transition. It will continue to evolve to drive forward the sustainability agenda.
We believe the badge will provide credible recognition of impactful sustainability efforts for more properties worldwide and provide travelers with a transparent, consistent and easy-to-understand way to identify a wider range of more sustainable stays.

With our programme we will make sustainability more appealing and accessible to even the smallest accommodations by:
A free, large-scale, trusted and easy to understand sustainability label which matches traveller intent (see page 5 of our most recent Sustainable Travel Report) while reducing some key barriers for sustainability adoption for SME tourism accommodation providers (such as investment, information gaps or time to implement), increasing the likelihood that more accommodations can and will enhance their sustainability offering. 
Tailoring the sustainability journey and support provided to reflect the more limited resources and investment often available to SME accommodations.
Providing alternative approaches to assessing the sustainability of an accommodation e.g verified through a combination of innovative tools including customer reviews, on-site checks and AI, and thereby breaking down the cost barrier to certification.
Since its launch date +116.000 properties now have the badge and hundred of thousands properties now participate in the Travel Sustainable program. Going forward, we will continue to expand our existing Travel Sustainable Handbook and sustainability education programs for accommodations to tailor support based on their maturity level and local context.
Measurable targets: 
- After establishing a baseline in 2022, we will announce a target for sustainable bookings made by our customers in 2023. 
- Launch and evolve the Travel Sustainable program for accommodations, cars, rides and flights by the end of 2023