Economic values of mental health benefits from nature can provide a new conservation tool. Here we calculate valuations from increased workplace productivity and reduced healthcare spending. Visiting national parks buffers workplace productivity against mental health losses. In Australia, for visits at least monthly, productivity increases are up to 11 %, with weighted mean 4.6 %. Total contribution across all visit frequencies is ~1.8 % of GDP. In Australia, visiting protected areas improves individual mental health by up to 17 %, with weighted mean effect 1.80 % for mentally healthy and 4.44 % for mentally unhealthy visitors. These effects reduce direct healthcare costs by a further ~0.6 % of GDP. Scaling up worldwide via GDP, with adjustments for park visitation rates, per capita healthcare costs, and distributions of mental health indicators, yields an estimated global health services value of protected areas, via productivity and healthcare costs alone, of ~US$2.1 trillion per annum. During 2020–2022, nature deprivation reduced mental health worldwide. Employers and health insurers would gain from increase budgets for national parks. There are mental healthcare programs relying on parks in at least 6 nations. Research priorities include mechanisms and duration of health benefits, cf components and intensity of nature experiences, including biodiversity.