Unstable, unhealthy and poorly managed terrestrial ecosystems have direct implications on the quantity and quality of water available for human consumption and sanitation, SDG 6 (Clean water and sanitation for all). Ecosystems in a good ecological condition can sustain life and offer provisioning and regulating services (NBA, 2018). Anthropogenic activities are one of the many key pressures which negatively alter terrestrial ecosystems services.  Thus, recessions in efforts toward attaining SDG 15 can be directly associated with regressions in the availability of clean water (SDG 6). That is to say, with increased terrestrial ecosystem degradation in the forms of pollution, urbanisation, overexploitation (tragedy of the commons) and deforestation etc. there will be a reduction in the amount of safe water that is available for human use. This is a sentiment that is shared by Reid and Co (2017), that if the foundation, being SDG 14 and 15, is to crumble, be altered or become unstable, all the other SDG’s, which rely on healthy functioning ecosystems will inevitably deteriorate. Therefore, the maintenance, as well as protection of terrestrial ecosystems, are essential for water security and attaining the sustainable development goals.

The Bureau of Reclamation outlined that 71% of the planet is covered with water, however, only 3% of that is freshwater which is fit for human consumption, of which more than two-thirds (83%) are frozen as ice glaciers and unavailable for use. SDG 6 is aimed at attempting to mitigate the global effects of water scarcity, as access to clean water is essential for the survival of humans, the economy and animals on Earth (Guppy et al., 2019). According to the WHO (2018) by 2025 two-thirds of the world will have difficulty accessing clean water. For this reason, the preservation and protection of freshwater ecosystems is essential. Inland aquatic ecosystems are a source of water for societal and economic use, thus large amounts of water are required to remain within these ecosystems to ensure their health and continued provision of services (UN-WATER, 2021). That is because healthy ecosystems offer protection to the quantity and quality of freshwater. SDG 6 is therefore vital, as the lack of clean water is related to human deaths by water-borne diseases and the lack of food security, leading to hunger for subsistence farmers and decreased/exhausted income for the commercial farmers as crop farming is not viable without clean water supply (UN-WATER, 2021). The lack of crop cultivation will in turn result in bare land which is more susceptible to degradation. Thus interlinkages exist between SDG 6 and SDG 15, to safeguard the inland water ecosystems as to ensure that they remain healthy(natural or near-natural) and resilient (UN-WATER, 2021).