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partly because nature-based sectors are becoming less dependent
on unmitigated natural infl uences.
• This point then raises a fourth and deeper issue regarding im-
pacts. If our societies do indeed evolve and grow rapidly over the
coming decades, as is projected by all economic and climate mod-
els, how can we forecast the impacts on those different structures
a century or more from now? Assessment is diffi cult because tech-
nological change is rapid in areas such as agriculture, human
health, and migration. Assessing the shape of our economies and
making reliable impacts analysis in the distant future is like view-
ing a landscape through a fuzzy telescope.
• As a fi nal point, we found that the most troubling impacts are in
areas that are far removed from the market and thus from human
management. This point applies particularly to areas such as hu-
man and natural treasures, ecosystems, ocean acidifi cation, and
species. Valuing the impacts in these areas is doubly challenging
because of the diffi culty of estimating impacts and the lack of re-
liable techniques for measuring impacts. Economics can contrib-
ute least in areas where we need it most.
VULNERABILITY BY ECONOMIC SECTOR
With these observations about individual sectors behind us, let's
look at the overall picture. We do this fi rst for the market economy of
the United States for the period 1948-2011. The industrial composition
of the United States is representative of high-income countries today,
and it is likely that middle-income countries will have a similar struc-
ture by the middle of this century.
For this purpose, I have classifi ed U.S. industries into three groups:
heavily impacted sectors, moderately impacted sectors, and lightly or
dicate that the heavily affected or vulnerable sectors are likely to be
agriculture and forestry. In these sectors, productivity might decline
substantially under extreme scenarios (recall the discussion about agri-
culture in Chapter 7 as well as the yield diagram in Figure 14).
