Tuesday, October 5th, 2010
When we think of human population change and resource use, it’s easy to assume that more people will consume more resources, such as water, energy, and food. An important corollary is that resource limitations will limit population growth. Thomas Malthus was perhaps the most influential proponent of this idea.
However, several factors complicate this story:
(1) Affluence is a multiplier such that more people in a wealthy, high-consumption society lead to a disproportionate use of resources compared to people in poor countries. As my recent article on global change in Nature Knowledge shows,
the populations of China and India are roughly 1.32 and 1.14 billion people, respectively — about four times that of the US. However, the energy consumption per person in the US is six times larger than that of a person in China, and 15 times that of a person in India. Because the demand for resources like energy is often greater in wealthy, developed nations like the US, this means that countries with smaller populations can actually have a greater overall environmental impact. Over much of the past century, the US was the largest greenhouse gas emitter because of high levels of affluence and energy consumption. In 2007, China overtook the US in terms of overall CO2 emissions as a result of economic development, increasing personal wealth, and the demand for consumer goods, including automobiles.
(2) Interestingly, resource limitations may actually inhibit our ability to slow population growth. Yes, you read that right. A new paper by John DeLong and colleagues in this week’s PLOS One (open access) argues exactly this. Here’s why:
Influential demographic projections suggest that the global human population will stabilize at about 9–10 billion people by mid-century. These projections rest on two fundamental assumptions. The first is that the energy needed to fuel development and the associated decline in fertility will keep pace with energy demand far into the future. The second is that the demographic transition is irreversible such that once countries start down the path to lower fertility they cannot reverse to higher fertility. Both of these assumptions are problematic and may have an effect on population projections. Here we examine these assumptions explicitly. Specifically, given the theoretical and empirical relation between energy-use and population growth rates, we ask how the availability of energy is likely to affect population growth through 2050. Using a cross-country data set, we show that human population growth rates are negatively related to per-capita energy consumption, with zero growth occurring at ~13 kW, suggesting that the global human population will stop growing only if individuals have access to this amount of power. Further, we find that current projected future energy supply rates are far below the supply needed to fuel a global demographic transition to zero growth, suggesting that the predicted leveling-off of the global population by mid-century is unlikely to occur, in the absence of a transition to an alternative energy source. Direct consideration of the energetic constraints underlying the demographic transition results in a qualitatively different population projection than produced when the energetic constraints are ignored. We suggest that energetic constraints be incorporated into future population projections.
I love these kinds of unexpected outcomes that make us think more critically about simplified assumptions when it comes to the drivers and impacts of global change.
DeLong, J., Burger, O., & Hamilton, M. (2010). Current Demographics Suggest Future Energy Supplies Will Be Inadequate to Slow Human Population Growth PLoS ONE, 5 (10) DOI: 10.1371/journal.pone.0013206
Photo credit: wili_hybrid
Saturday, September 11th, 2010
Here’s an interesting thought question: How much would global temperature warm if we used only the existing energy infrastructure (i.e., power plants, furnaces, motor vehicles) until these machines reached the end of their useful lives? Once they died, they would be replaced by devices that did not emit CO2.
Steven Davis and colleagues addressed this question in the current issue of Science:
We calculated cumulative future emissions of 496 (282 to 701 in lower- and upperbounding scenarios) gigatonnes of CO2 from combustion of fossil fuels by existing infrastructure between 2010 and 2060, forcing mean warming of 1.3°C (1.1° to 1.4°C) above the pre-industrial era and atmospheric concentrations of CO2 less than 430 parts per million. Because these conditions would likely avoid many key impacts of climate change, we conclude that sources of the most threatening emissions have yet to be built. However, CO2-emitting infrastructure will expand unless extraordinary efforts are undertaken to develop alternatives.
Their analysis suggests that CO2 emissions would decline linearly from 35 gigatons/year in 2010 to less than 5 gigatons/year in 2050, with the majority of the remainder being non-energy emissions from things like cement manufacture and land use changes.
On a personal level, this would mean replacing your current furnace, car, and electricity sources with ones that emitted no CO2, so we’re talking upwards of 15-20 years for a personal vehicle, 20-30 years for a furnace, and 50+ years for power stations, depending on the age of these items. The average power plant age in the U.S. is 32 years compared to 12 years in China and 21 and 27 years in Japan and Europe.
It’s encouraging to know that it may be possible to avert serious climate change without having to shut down existing infrastructure right away (especially long-lived fossil fuel power plants) but only if we plow significant funding into developing and implementing carbon-free technologies to replace them. However, Davis et al. acknowledge that this is a tall order:
[T]here is little doubt that more CO2-emitting devices will be built. Our analysis considers only devices that emit CO2 directly. Substantial infrastructure also exists to produce and facilitate use of these devices. For example, factories that produce internal combustion engines, highway networks dotted with gasoline refueling stations, and oil refineries all promote the continuation of oil-based road transport emissions. Moreover, satisfying growing demand for energy without producing CO2 emissions will require truly extraordinary development and deployment of carbon-free sources of energy, perhaps 30 TW by 2050. Yet avoiding key impacts of climate change depends on the success of efforts to overcome infrastructural inertia and commission a new generation of devices that can provide energy and transport services without releasing CO2 to the atmosphere.
Davis, S., Caldeira, K., & Matthews, H. (2010). Future CO2 Emissions and Climate Change from Existing Energy Infrastructure Science, 329 (5997), 1330-1333 DOI: 10.1126/science.1188566
Photo credit: Stuck in Customs
Saturday, September 11th, 2010
This week’s issue of Science includes a special section on biodiversity. A review article by Michael Rands and colleagues, Biodiversity Conservation: Challenges Beyond 2010, summarizes the current approaches and challenges for conservation.
Here is an excerpt describing their outlook for the future:
The challenges of addressing the social and behavioral contexts for biodiversity conservation are daunting. We are far from including biodiversity in our conventional measures of well-being, which focus on wealth creation and internationally
recognized estimates of GDP. Although there have been attempts to redefine these (including, for instance, the Human Development Index and green national accounts), the mainstream view of well-being and of national development remains focused on narrowly defined economic growth. Furthermore, the current recession only strengthens the emphasis on growth. The transition to sustainability will not be easy, but it is central to securing a future for biodiversity. Conservation strategies, in concert with other environmental policies, must address seemingly intractable and politically unpalatable issues. In both developed and emerging economies, we need to reduce the carbon and material throughput demanded by current patterns of production and consumption if we are to create viable and democratically acceptable trajectories of contraction and convergence in resource use. In parallel, we must recognize that successful human development agendas are underpinned by functional ecosystems, and by biodiversity. This is the year in which governments, business, and civil society could decide to take seriously the central role of biodiversity in human well-being and quality of life and to invest in securing the sustainable flow of nature’s public goods for present and future generations.
Photo credit: Feuillu
Saturday, December 12th, 2009
That’s the title of a new article1,2 by Terry Chapin and colleagues in a forthcoming issue of Trends in Ecology and Evolution.
Human actions are having large and accelerating effects on the climate, environment and ecosystems of the Earth, thereby degrading many ecosystem services. This unsustainable trajectory demands a dramatic change in human relationships with the environment and life-support system of the planet. Here, we address recent developments in thinking about the sustainable use of ecosystems and resources by society in the context of rapid and frequently abrupt change.
To deal with these challenges, they advocate “ecosystem stewardship,” which has three core principles. Here are excerpts of these principles (slightly condensed/adapted by me); please check out the paper for details:
Thursday, December 10th, 2009
We don’t ordinarily think about climate change and land use change as being a synergistic threat to society. However, the combination of impervious surfaces that increase runoff, declining wetlands, levees, and more severe storms pack a quadruple whammy that could lead to some major flooding in the future. From the cool adaptation work done in Keene, NH, we know that much of our infrastructure (roads, bridges, culverts) can’t handle the added stress of streams and rivers with higher discharge. We’re looking at a potential nightmare of increased costs associated with infrastructure damage.
In this week’s issue of Science, Jeffrey Opperman and colleagues argue1 that our historical paradigm of flood control with levees needs to fundamentally change to achieve a more sustainable socioecological system.
Their solution? Tear down some of the levees to allow some floodplains to flood. This can accomplish several goals:
(1) Flood risk reduction
(2) Increased floodplain goods and services
(3) Building resiliency to climate change
Opperman and colleagues acknowledge that there are political hurdles, such as convincing some private landowners that flooding their land can be useful.
But there are creative solutions that have already been deployed. They cite Sacramento as an example: Some farmers allow their crops to flood, serving as a pressure-relief valve when rivers swell, thereby preventing more expensive damage. In return, the farmers are compensated for their crop loss. It’s a win-win situation that presumably costs less than dealing with infrastructure damage or having to build new infrastructure that handles greater flooding.
Another idea is to allow some of these areas to become wetlands and compensate people as part of a wetlands banking system to mitigate the loss of wetlands elsewhere. This would most likely have several ecological benefits, including increasing habitat for wetland-dependent species such as waterfowl and other migrating birds. It would also likely increase vegetation productivity and carbon storage.
It’s interesting to note that they don’t call for an end to economic activity or human use in floodplains. Sure, we probably want to stop building McMansions in flood-prone regions. However, there are several ways we can use floodplains for ecological and economic benefit. These will likely require compensation, but in the long run, it’s cheaper than having to re-tool major infrastructure to handle greater discharge with climate warming.
1Opperman, J.J. et al (2009) Sustainable floodplains through large-scale reconnections to rivers. Science 326:1487-1488.
Wednesday, December 2nd, 2009
Most of the focus these days is on how we can mitigate climate warming by achieving specific reductions targets like 20% by 2020 and 80% by 2050. Economists from McGill University, Isabel Galiana and Christopher Greene, are going to stir up debate in their latest paper1 in Nature by arguing that the current way of thinking about mitigating warming needs to be turned on its head.
Focusing on rapid emissions reductions, they say, may not be the best way to rapidly stabilize climate as cheaply as possible. They even go as far as to say that climate can be stabilized at a 2 degree C warming even if most of the carbon reductions don’t happen until after 2050.
What’s the basis for their argument? Technology-led approaches. Let’s see what this means…
Friday, November 13th, 2009
There’s a new website/journal called Solutions, edited by Bob Costanza, David Orr, Paul Hawken, and John Todd that’s worth looking taking a look at.
Monday, November 9th, 2009
Let’s take a look at five innovative and exciting ideas from Stanford University, City College of New York, Western Michigan University, UC-Davis, and the University of Arizona…