Nature International Weekly journal of Science. Look under 'Jobs and Careers'. A few are in natural resources. The site is searchable by country, subject, etc. This is a growing index, so check often.
Updates are weekly.
Ag Research Service Listing of current openings under 'Employment Opportunities' with this government department. In Frames, Look under 'More', then select 'Employment Opportunities'. Some of the jobs listed are in the natural resources fields. Its a real variety of science jobs, so it is a matter of timing whether a job your interested in would be posted. It includes links to faculty, staff, and administrative announcements and is not restricted to teaching positions.