Feedbacks From Ecosystem Pressure

Here's a quote from the IPCC WG2 TAR Chapter 5:

The Earth is being subjected to many human-induced and natural

changes, often referred to as global change. These changes

include pressures from increased demand for resources driven

by economic growth, increased human population, land-use

and land-cover change, the accelerated rate of anthropogenic

nitrogen production and other air pollutants, and urbanization

and industrialization; resulting fossil fuel emissions contribute

to a discernible impact on global climate

The model used by the IPCC to understand global change is the State-Pressure-Response (SPR) model from the Organization for Economic Cooperation and Development (OECD):

In the SPR model, "state" refers to the current state of the ecosystem, "pressure" includes direct and indirect human pressure and "adaption" includes automatic ecosystem adaptions and deliberate human adaptions to changes.

What I would add to this model is a feedback from "state" to "pressure", that is, if ecosystems deteriorate, it will have an impact on human-induced pressures (imagine a Malthusian catastrophe where population growth outruns the ability of ecosystems to support the population--the IPCC has been careful not to introduce catastrophes into their modeling so the feedback loop is missing).

To make the SPR model a little more specific, substitute "economic growth" for "pressure," ecosystem "Biodiversity" for state and limit consideration to "Economic Responses." According to the IPCC, economic growth reduces biodiversity. However, biodiversity is needed for economic growth (consider the effects of soil degradation on agricultural productivity) even though ecosystems are almost never included as an input to economic growth models. The questions is, what will be the economic response? Physical capital cannot be substituted for ecosystem services (tried and failed in Biosphere 2). The impact will probably not be positive!

What is the current status of ecosystems? The Living Planet Index developed by WWF shows that after a peak in the mid-1970's (during the OPEC oil crisis and resulting environmental response), biodiversity has been declining. What's your best guess about when we'll see the economic response, if it hasn't happened already.