• Energy Research

New approach proposed for defining preconditions for human development Crossing certain biophysical thresholds could have disastrous consequences for humanity Three of nine interlinked planetary boundaries have already been overstepped

Carbon accumulation in the terrestrial biosphere could partially offset the effects of anthropogenic CO2 emissions on atmospheric CO2. The net impact of increased CO2 on the carbon balance of terrestrial ecosystems is unclear, however, because elevated CO2 effects on carbon input to soils and plant use of water and nutrients often have contrasting effects on microbial processes. Here we show suppression of microbial decomposition in an annual grassland after continuous exposure to increased CO2 for five growing seasons. The increased CO2 enhanced plant nitrogen uptake, microbial biomass carbon, and available carbon for microbes. But it reduced available soil nitrogen, exacerbated nitrogen constraints on microbes, and reduced microbial respiration per unit biomass. These results indicate that increased CO2 can alter the interaction between plants and microbes in favour of plant utilization of nitrogen, thereby slowing microbial decomposition and increasing ecosystem carbon accumulation.

We reviewed existing and planned adaptation activities of federal, tribal, state, and local governments and the private sector in the United States (U.S.) to understand what types of adaptation activities are underway across different sectors and scales throughout the country. Primary sources of review included material officially submitted for consideration in the upcoming 2013 U.S. National Climate Assessment and supplemental peer-reviewed and grey literature. Although substantial adaptation planning is occurring in various sectors, levels of government, and the private sector, few measures have been implemented and even fewer have been evaluated. Most adaptation actions to date appear to be incremental changes, not the transformational changes that may be needed in certain cases to adapt to significant changes in climate. While there appear to be no one-size-fits-all adaptations, there are similarities in approaches across scales and sectors, including mainstreaming climate considerations into existing policies and plans, and pursuing no- and low-regrets strategies. Despite the positive momentum in recent years, barriers to implementation still impede action in all sectors and across scales. The most significant barriers include lack of funding, policy and institutional constraints, and difficulty in anticipating climate change given the current state of information on change. However, the practice of adaptation can advance through learning by doing, stakeholder engagements (including “listening sessions”), and sharing of best practices. Efforts to advance adaptation across the U.S. and globally will necessitate the reduction or elimination of barriers, the enhancement of information and best practice sharing mechanisms, and the creation of comprehensive adaptation evaluation metrics.

Understanding links between the disturbance regime and regional climate in boreal regions requires observations of the surface energy budget from ecosystems in various stages of secondary succession. While several studies have characterized fire‐induced differences in surface energy fluxes from boreal ecosystems during summer months, much less is known about these differences over the full annual cycle. Here we measured components of the surface energy budget (including both radiative and turbulent fluxes) at three sites from a fire chronosequence in interior Alaska for a 1‐year period. Our sites consisted of large burn scars resulting from fires in 1999, 1987, and ∼1920 (hereinafter referred to as the 3‐, 15‐, and 80‐year sites, respectively). Vegetation cover consisted primarily of bunch grasses at the 3‐year site, aspen and willow at the 15‐year site, and black spruce at the 80‐year site. Annual net radiation declined by 31% (17 W m−2) for both the 3‐ and the 15‐year sites as compared with the 80‐year site (which had an annual mean of 55 W m−2). Annual sensible heat fluxes were reduced by an even greater amount, by 55% at the 3‐year site and by 52% at the 15‐year site as compared with the 80‐year site (which had an annual mean of 21 W m−2). Absolute differences between the postfire ecosystems and the mature black spruce forest for both net radiation and sensible heat fluxes were greatest during spring (because of differences in snow cover and surface albedo), substantial during summer and winter, and relatively small during fall. Fire‐induced disturbance also initially reduced annual evapotranspiration (ET). Annual ET decreased by 33% (99 mm yr−1) at the 3‐year site as compared with the 80‐year site (which had an annual flux of 301 mm yr−1). Annual ET at the 15‐year site (283 mm yr−1) was approximately the same as that from the 80‐year site, even though the 15‐year site had substantially higher ET during July. Our study suggests that differences in annual ET between deciduous and conifer stands may be smaller than that inferred solely from summer observations. This study provides a direct means to validate land surface processes in global climate models attempting to capture vegetation‐climate feedbacks in northern terrestrial regions.

This article presents governance and institutional strategies for climate-induced community relocations. In Alaska, repeated extreme weather events coupled with climate change-induced coastal erosion impact the habitability of entire communities. Community residents and government agencies concur that relocation is the only adaptation strategy that can protect lives and infrastructure. Community relocation stretches the financial and institutional capacity of existing governance institutions. Based on a comparative analysis of three Alaskan communities, Kivalina, Newtok, and Shishmaref, which have chosen to relocate, we examine the institutional constraints to relocation in the United States. We identify policy changes and components of a toolkit that can facilitate community-based adaptation when environmental events threaten people’s lives and protection in place is not possible. Policy changes include amendment of the Stafford Act to include gradual geophysical processes, such as erosion, in the statutory definition of disaster and the creation of an adaptive governance framework to allow communities a continuum of responses from protection in place to community relocation. Key components of the toolkit are local leadership and integration of social and ecological well-being into adaptation planning.

Ecosystem stewardship is an action-oriented framework intended to foster the social-ecological sustainability of a rapidly changing planet. Recent developments identify three strategies that make optimal use of current understanding in an environment of inevitable uncertainty and abrupt change: reducing the magnitude of, and exposure and sensitivity to, known stresses; focusing on proactive policies that shape change; and avoiding or escaping unsustainable social-ecological traps. As we discuss here, all social-ecological systems are vulnerable to recent and projected changes but have sources of adaptive capacity and resilience that can sustain ecosystem services and human well-being through active ecosystem stewardship.

Ecosystems influence climate through multiple pathways, primarily by changing the energy, water, and greenhouse-gas balance of the atmosphere. Consequently, efforts to mitigate climate change through modification of one pathway, as with carbon in the Kyoto Protocol, only partially address the issue of ecosystem–climate interactions. For example, the cooling of climate that results from carbon sequestration by plants may be partially offset by reduced land albedo, which increases solar energy absorption and warms the climate. The relative importance of these effects varies with spatial scale and latitude. We suggest that consideration of multiple interactions and feedbacks could lead to novel, potentially useful climate-mitigation strategies, including greenhouse-gas reductions primarily in industrialized nations, reduced desertification in arid zones, and reduced deforestation in the tropics. Each of these strategies has additional ecological and societal benefits. Assessing the effectiveness of these strategies requires a more quantitative understanding of the interactions among feedback processes, their consequences at local and global scales, and the teleconnections that link changes occurring in different regions.