Marl, who worked in Elsevier's material science and engineering division, has been brought in to promote the launch of the charity in Europe.
She will also attempt to build the charity's profile with British businesses and the scientific community, as well as with the general public.
The charity is looking to increase its support and funding and to encourage scientists to apply for help to finance their conservation projects.
'When people think of environmental charities, we want them to think of Earthwatch,' said Marl.
She replaces Susie Duncan, who left in March, and will lead a seven-strong team, reporting to director of programme operations Eve Carpenter.
European communications will be led by Marl from the UK office. It is the first job she has taken in the voluntary sector.
In addition to its UK operation, Earthwatch has offices in the US, Australia and Japan.