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Abstract

The Pope has made a strong call for action on climate change, but it fails to address the complex linkages between sustainable development and demographic growth.
904 NATURE CLIMATE CHANGE | VOL 5 | OCTOBER 2015 | www.nature.com/natureclimatechange
OPINION & COMMENT | FOCUS
COMMENTARY:
Biophysical limits, women’s
rights and the climate encyclical
Paul R. Ehrlich and John Harte
The Pope has made a strong call for action on climate change, but it fails to address the complex
linkages between sustainable development and demographic growth.
The Popes recent encyclical on climate
change is a passionate and compelling
call for dramatic changes in society to
match the global changes in the environment
that threaten the future of human civilization
as we know it (http://go.nature.com/7IbiB5).
But it overlooks a crucial incompatibility
at the heart of the climate change
problem: marrying shared and sustainable
development with demographic growth.
e encyclical’s narrow perspective is
revealed in the following excerpt: “Instead
of resolving the problems of the poor and
thinking of how the world can be dierent,
some can only propose a reduction in the
birth rate. At times, developing countries
face forms of international pressure which
make economic assistance contingent on
certain policies of ‘reproductive health’. Yet
while it is true that an unequal distribution
of the population and of available resources
creates obstacles to development and a
sustainable use of the environment, it must
nonetheless be recognized that demographic
growth is fully compatible with an integral
and shared development. To blame
population growth instead of extreme and
selective consumerism on the part of some, is
one way of refusing to face the issues” (§50).
A close look at the full complexity of the
interconnected demographic, biophysical,
economic, and social dimensions of the
global environmental situation suggests
that demographic growth is not compatible
with either shared development or with a
sustainable environment. e encyclical
portrays a world in which a real choice exists
between confronting population growth on
the one hand, and avoiding that option by
more equitably distributing resources on
the other.
Attempts to frame the issue as solvable
by either more equitable distribution or by
restricting the number of people miss two
essential factors that link these diering
viewpoints. One is the ever-dwindling pool of
resources and ecosystem services as a result
of the demands of a growing population
on the environment. e second is the
increasing diculty of achieving the forms
of governance needed to more equitably
distribute resources on an ever more
crowded planet.
Population growth
Demographic trends along with rampant
consumption by the rich are the major
drivers of environmental degradation.
More people using more fossil fuels means
more climate change; more people eating
more food means more land conversion
(with associated loss of biodiversity), more
overdra of groundwater for irrigation,
and more pressure on threatened marine
resources; and more people consuming more
material goods potentially means more toxic
waste products and more mining.
People today and their children, no
matter where they are born, will put even
more pressure on the environment than in
the past due to demand for virtually every
resource, from agricultural land and water
to copper and oil. Human beings are smart
and pick the low-hanging fruit rst: they
farm the richest soils rst, drink the cleanest
and closest water rst, and tap the shallowest
pools of oil rst. ey exploit the resources
that are cheapest and that generally result in
the least environmental impact rst.
As more people consume more resources,
humanity is le with poorer quality, more
expensive resources, the exploitation of which
causes more harm. For example, when people
rst became interested in copper it was lying
around on the surface — almost pure in some
places. Now, using much more commercial
energy, it is mined at depths of almost two
miles where ores are three per cent copper or
less, with greater consequent environmental
impacts per pound produced.
Moreover, as population and consumption
degrade air, water and soil quality, as well
as climate and biodiversity, the damages act
upon each other in a manner that reinforces
the deterioration1,2. us global warming
threatens forests and biodiversity, while
forest degradation and biodiversity loss alter
climate and threaten water supply, air quality
and soil fertility. Soil loss and desertication
force farmers to exploit more marginal
lands, resulting in yet more erosion, greater
need for irrigation water, fertilizers, and
herbicides, and more clear-cutting of valuable
habitat, all contributing to further loss of
biodiversity. More energy intensive methods
of compensating for any of the above damage
results in greater disturbance of the climate
and pollutes the air and water.
But those kinds of destructive linkages
arise not only from biophysical factors.
Demographic, environmental and
institutional factors are deeply interconnected,
further adding to the dilemma. From villages
to nations, egalitarian systems of governance
and resource distribution do not ourish
when communities lack basic resources. Great
inequalities in wealth or income can aect
governance systems, leading (for example),
to the nutritional needs of the poor not being
properly met. Well-nanced attempts to
DORLING KINDERSLEY / THINKSTOCK
© 2015 Macmillan Publishers Limited. All rights reserved
NATURE CLIMATE CHANGE | VOL 5 | OCTOBER 2015 | www.nature.com/natureclimatechange 905
FOCUS | OPINION & COMMENT
reduce or terminate programs to feed the poor
in the United States demonstrate how sound
governance can be undermined by the rich.
Resource scarcity
Human numbers are overwhelming critical
infrastructure, in many, if not most, areas,
as ecological deterioration and even
devastation is simultaneously reducing many
peoples’ means of subsistence. Under such
circumstances people have less time to seek
social justice because they must spend more
time focusing on survival. Inundated island
nations in the Pacic and Indian Oceans,
and the rising ood of refugees crossing the
Mediterranean, provide just a tiny preview of
how these pressures will play out.
e prospects for future global food
security exemplify this situation. Contrasting
insucient food versus inequitably
distributed food may seem a caricature but
as the encyclical reminds us, discussions
on sustainability oen polarize into these
seemingly opposing viewpoints.
Despite the general agreement on many
of the ecological challenges, discussions on
sustainability oen divide experts about
whether the solution lies in dealing with
population growth and consumption, or
making food distribution more equitable.
is is also true of those who argue that it is
consumption alone that results in excessive
carbon emissions. Focusing on only half the
source of, or half the potential solution to, a
complex problem can be nearly as ineective
as ignoring the problem altogether, when both
factors jointly determine the outcome.
Policymakers and the academic
community must recognize that equity
issues make adequately feeding everyone
extremely dicult. But they must also
recognize that biophysical constraints limit
our ability to feed more than a certain
number of people, even under the most
equitable of distributional arrangements.
Most importantly, they must acknowledge
that our biophysical and social dilemmas
are tightly linked, and that as population
grows the capacity of social systems to
deal with the tightening biophysical
constraints shrinks.
e basic task of supplying the
populations needs for calories and
nutrients is not being met now. Some
800 million of today’s 7.3 billion people are
undernourished and perhaps half of the
world’s people — most, but not all, in poor
and middle-income nations — lack access to
one or more essential nutrients3,4. Even when
adequate calories are available, diets are
oen far from ideal, increasing the burden
of disease. Indeed, inadequate consumption
of fruits, nuts, seeds, and vegetables makes a
major contribution to ill health worldwide.
In short, current struggles to feed humanity
make the prospects seem slim for the
expected 9.7 billion people in 2050 to be
healthy and have adequate nutrition — and
perhaps billions more beyond that5,6.
As abhorrent as our current resource
inequities are, they could pale in comparison
with the impending inequity between
those alive today and those who will
be born tomorrow. Future populations,
under current trends, will inherit a rapidly
deteriorating planetary life support system.
We envision no quick xes or shortcuts.
ose who champion increased equality as
a means of achieving global food security
must team up with those who urge curbing
over-consumption and humane transitioning
to a much reduced and thus sustainable
population. Otherwise, the new political and
economic institutions desperately needed
to redirect humanity toward sustainable
food security and away from the ction of
perpetual growth will not evolve.
Pope Francis needs to heed his own
comments7 on the Churchs “obsession” with
contraception and abortion, and assume a
leadership position in support of women’s
rights and family planning. ere is little
chance that the existential challenge facing
humanity will be met if the call for dramatic
change in society is not expanded to embrace
the global demographic dilemma.
Paul R. Ehrlich is in the Department of Biology,
Stanford University, Stanford, California 94305, USA.
John Harte is at the Energy and Resources Group,
University of California, Berkeley, California 94720,
USA. e-mail: pre@stanford.edu
References
1. Barnosky, A. etal. Nature 486, 53–58 (2012).
2. Harte, J. Biodivers. Conserv. 5, 1069–1083 (1996).
3. Myers, S. etal. Nature 510, 139–142 (2014).
4. Tilman, D. & Clark, M. Nature 515, 518–522 (2014).
5. Ehrlich, P. & Ehrlich, A. Proc. R.Soc. B 280, 20122845 (2013).
6. Ehrlich, P. & Harte, J. Int. J.Environ. Stud.
http://dx.doi.org/10.1080/00207233.2015.1067468 (2015).
7. Goodstein, L. Pope says Church is ‘obsessed’ with gays, abortion
and birth control. e New York Times (19 September 2013);
http://go.nature.com/JQqQaj
COMMENTARY:
The Pope’s encyclical as a call
for democratic social change
Anabela Carvalho
The climate change encyclical represents a decisive democratic act. It calls on citizens to challenge
dominant politics, power, and consumer culture in the name of tackling one of the world’s great
socio-environmental issues.
The Pope’s climate change encyclical
(http://go.nature.com/7IbiB5)
injects democratic politics into the
environmental crisis by showing how it is tied
to wider sociocultural processes at the heart
of modern societies. rough an integrative
critical analysis, the encyclical reclaims
climate change from the exclusionary realm
of technocracy and political–economic elites
and calls for an “honest and open debate so
that particular interests or ideologies will not
prejudice the common good” (§188).
e words dialogue, debate and
discussion are found throughout the
document: from the Popes expressed aim
of inclusive conversation (“I would like to
enter into dialogue with all people about
our common home” (§3)), to his call for
© 2015 Macmillan Publishers Limited. All rights reserved
... where parameter D = D p /D u is the ratio of the diffusion coefficients. In its turn, it appears that a necessary condition for (23) is that F u and G p must be of different sign. Consider F u > 0 and G p < 0; in this case, u is called the "activator" and p the "inhibitor" [21]. ...
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... where parameter D = D p /D u is the ratio of the diffusion coefficients. In its turn, it appears that a necessary condition for (23) is that F u and G p must be of different sign. Consider F u > 0 and G p < 0; in this case, u is called the "activator" and p the "inhibitor" [21]. ...
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  • P Ehrlich
  • A Ehrlich
Ehrlich, P. & Ehrlich, A. Proc. R. Soc. B 280, 20122845 (2013).
  • S Myers
Myers, S. et al. Nature 510, 139-142 (2014).
  • A Barnosky
Barnosky, A. et al. Nature 486, 53-58 (2012).
Pope says Church is 'obsessed' with gays, abortion and birth control <http://go.nature.com/JQqQaj>
  • L. Goodstein
Goodstein, L. Pope says Church is 'obsessed' with gays, abortion and birth control. The New York Times (19 September 2013);