Assessing human impacts on Marine ecosystems

Abstract

Human society derives considerable benefit from marine ecosystems, as described in Chapters 1 and 2. It does so through a wide range of activities. In deriving these benefits humans exploit a range of ecological and environmental resources and services (Chapter 2). The majority of human uses of the marine environment have some measurable impact on the supporting ecosystem (Figure 3.1). Our treatment of these impacts starts from a consideration of the benefits human society is deriving from the system but recognises that the process of obtaining many of these benefits is carried out by what can be termed ‘economic sectors': fishing, construction, agriculture, tourism, etc. (Table 3.1). Impacts are direct or indirect and may be sustainable, in which case the system will continue to provide the service indefinitely and will recover upon cessation of the impacting activity, or they may be unsustainable (Frid and Dobson, 2013). Human activities may extract living components of the ecosystem (for example, as food or for the aquarium trade), non-living materials (salt, sediment, mineral deposits), and both sustainable (wind, tides) and unsustainable (oil, gas) energy resources. In each of these cases the system is altered by the removal (a direct effect) and often also by the removal process which may have direct and indirect effects on the ecosystem. Humans discharge their waste directly or indirectly (via rivers and agricultural runoff) into the seas and in doing so they exploit regulating services to, for example, dilute, transform, detoxify and sequester wastes (Peterson and Lubchenko, 1997). The cultural importance of natural systems is receiving increasing recognition for its support of the very profitable tourism, leisure and recreation sectors, as well as benefiting health and well-being.