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By Daniel Collins

Humans have depended on nature since we were knee-high to Australopithecus afarensis. Our ancestors drank river water, harvested berries from bushes and took refuge beneath trees. Today, we drink tap water, buy groceries from supermarkets and build houses out of trees. Over the two million intervening years, humans have increasingly co-opted and engineered natural ecosystems to meet their evolving needs (e.g., agriculture and hydropower), but we are still very much dependent on ecosystem services.

Ecosystem services are the direct and indirect benefits that we receive from ecosystems. They include the provision of food, water and minerals, regulation of natural hazards or pollination, support of nutrient cycling and seed dispersal, and the cultural services behind recreation and spiritual values.

Identifying an area’s ecosystem services is becoming a useful means of recognising and meeting competing environmental needs, and is the focus of the Royal Society of New Zealand’s recent issue paper (see the SMC press briefing here). The paper brings together scientists from around NZ to lay out what ecosystem services are all about and how they’re being incorporated into environmental management and research. As a concrete example, they draw on a Lincoln University study of the effects of the Opuha Dam in Canterbury (PDF).

An important point of the Opuha Dam study is that, over the 10 years since the dam was built, the ecosystem services provided by the Opihi River have changed. Water supply and flow regulation have tangibly improved, as intended. And while other ecosystem services can be identified — provision of salmon, erosion control, perceived beauty, mauri[1], etc — they are much harder to quantify. In fact, for the Opihi River, it is unclear whether many of the ecosystem services have improved or degraded. What is clear, though, is that by simply listing an area’s ecosystem services we can build a richer and collective picture of the various values that different parts of our society place on that area.

As Waiology is a hydrology blog, I want to highlight those ecosystem goods and services that relate specifically to the amount and movement of water. The RSNZ paper and the original report list several associated with the Opihi:

  • water supply for irrigation, drinking, industry and livestock;
  • hydroelectricity generation;
  • flow regulation (minimum flows, flushing flows);
  • flood and drought protection;
  • habitat for salmon, trout, mahika kai[2], flax and invasive plants; and
  • flow characteristics that underpin river bank stabilisation, boating, swimming, beauty and natural character.

Not surprisingly, there are few ecosystem services affected by reservoirs that are fully outside the domain of hydrology. I’ll elaborate on nature’s hydrological services in the near future.

In the end, ecosystem services offer a framework for examining resource use and environmental change. While the framework is not fully operational yet, it does help us to better understand how we use and modify natural resources.

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[1] Mauri = in Maori custom, the life force unique to a resource that includes both physical and spiritual attributes.
[2] Mahika kai or mahinga kai = food and resources gathering area (in te reo Maori).