Landscape Partnership Resources Library
WATER, CLIMATE CHANGE, AND FORESTS Watershed Stewardship for a Changing Climate
Water from forested watersheds provides irreplaceable habitat for aquatic and riparian species and supports our homes, farms, industries, and energy production. Secure, high-quality water from forests is fundamental to our prosperity and our stewardship responsibility. Yet population pressures, land uses, and rapid climate change combine to seriously threaten these waters and the resilience of watersheds in most places. Forest land managers are expected to anticipate and respond to these threats and steward forested watersheds to ensure the sustained protection and provision of water and the services it provides. Effective, constructive watershed stewardship requires that we think, collaborate, and act. We think to understand the values at risk and how watersheds can remain resilient, and we support our thinking with knowledge sharing and planning. We collaborate to develop common understandings and goals for watersheds and a robust, durable capacity for response that includes all stakeholders and is guided by science. We act to secure and steward resilient watersheds that will continue to provide crucial habitats and water supplies in the coming century by implementing practices that protect, maintain, and restore watershed processes and services.
Wildfire, Wildlands, and People: Understanding and Preparing for Wildfire in the Wildland-Urban Interface: Gen. Tech. Rep. RMRS-GTR-299. Fort Collins, CO. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 36 p.
Fire has historically played a fundamental ecological role in many of America’s wildland areas. However, the rising number of homes in the wildland-urban interface (WUI), associated impacts on lives and property from wildfire, and escalating costs of wildfire management have led to an urgent need for communities to become “fire-adapted.” We present maps of the conterminous United States that illustrate historical natural fire regimes, the wildland-urban interface, and the number and location of structures burned since 1999. We outline a sampler of actions, programs, and community planning and development options to help decrease the risks of and damages from wildfire. Key Words: wildfire, community planning, fire-adapted, wildland-urban interface, defensible space
The Myth of Smart Growth
“Smart growth” is an urban growth management strategy that applies planning and design principles intended to mitigate the impacts of continued growth. If properly applied, these principles represent a positive contribution to new urban development. However, the rhetoric of “smart growth” is that population levels and growth rates are not the problem; it’s merely a matter of how we grow. According to the “smart growth” program, if we are less wasteful and more efficient in our urban growth, we can keep growing and everything will work out fine. The “smart growth” approach is fundamentally pro-growth and does not envision an end to growth or a need to end growth. “Smart growth” is cast as a comprehensive solution, whereas it is merely a potential means of modestly reducing the environmental, social, and economic impacts of continued growth while failing to address its inevitable consequences. The “smart growth” formula has been used to discount and transform legitimate public concerns about the amount and pace of growth into a discussion about how we should best continue growing.
Interdependence of groundwater dynamics and land-energy feedbacks under climate change
Climate change will have a significant impact on the hydrologic cycle, creating changes in freshwater resources, land cover and land–atmosphere feedbacks. Recent studies have investigated the response of groundwater to climate change but do not account for energy feedbacks across the complete hydrologic cycle1,2. Although land-surface models have begun to include an operational groundwater-type component3–5, they do not include physically based lateral surface and subsurface flow and allow only for vertical transport processes. Here we use a variably saturated groundwater flow model with integrated overland flow and land-surface model processes6–8 to examine the interplay between water and energy flows in a changing climate for the southern Great Plains, USA, an important agricultural region that is susceptible to drought. We compare three scenario simulations with modified atmospheric forcing in terms of temperature and precipitation with a simulation of present-day climate. We find that groundwater depth, which results from lateral water flow at the surface and subsurface, determines the relative susceptibility of regions to changes in temperature and precipitation. This groundwater control is critical to understand processes of recharge and drought in a changing climate.
Space observations of inland water bodies show rapid surface warming since 1985
Surface temperatures were extracted from nighttime thermal infrared imagery of 167 large inland water bodies distributed worldwide beginning in 1985 for the months July through September and January through March. Results indicate that the mean nighttime surface water temperature has been rapidly warming for the period 1985–2009 with an average rate of 0.045 ± 0.011°C yr−1 and rates as high as 0.10 ± 0.01°C yr−1. Worldwide the data show far greater warming in the mid‐ and high latitudes of the northern hemisphere than in low latitudes and the southern hemisphere. The analysis provides a new independent data source for assessing the impact of climate change throughout the world and indicates that water bodies in some regions warm faster than regional air temperature. The data have not been homogenized into a single unified inland water surface temperature dataset, instead the data from each satellite instrument have been treated separately and cross compared. Future work will focus on developing a single unified dataset which may improve uncertainties from any inter‐satellite biases.
Quantifying the negative feedback of vegetation to greenhouse warming: A modeling approach
Several climate models indicate that in a 2 × CO2 environment, temperature and precipitation would increase and runoff would increase faster than precipitation. These models, however, did not allow the vegetation to increase its leaf density as a response to the physiological effects of increased CO2 and consequent changes in climate. Other assessments included these interactions but did not account for the vegetation down‐regulation to reduce plant’s photosynthetic activity and as such resulted in a weak vegetation negative response. When we combine these interactions in climate simulations with 2 × CO2, the associated increase in precipitation contributes primarily to increase evapotranspiration rather than surface runoff, consistent with observations, and results in an additional cooling effect not fully accounted for in previous simulations with elevated CO2. By accelerating the water cycle, this feedback slows but does not alleviate the projected warming, reducing the land surface warming by 0.6°C. Compared to previous studies, these results imply that long term negative feedback from CO2‐induced increases in vegetation density could reduce temperature following a stabilization of CO2 concentration.
Changes in winter precipitation extremes for the western United States under a warmer climate as simulated by regional climate models
We find a consistent and statistically significant increase in the intensity of future extreme winter precipitation events over the western United States, as simulated by an ensemble of regional climate models (RCMs) driven by IPCC AR4 global climate models (GCMs). All eight simulations analyzed in this work consistently show an increase in the intensity of extreme winter precipitation with the multi-model mean projecting an area-averaged 12.6% increase in 20-year return period and 14.4% increase in 50-year return period daily precipitation. In contrast with extreme precipitation, the multi-model ensemble shows a decrease in mean winter precipitation of approximately 7.5% in the southwestern US, while the interior west shows less statistically robust increases.
Climate commitment in an uncertain world
Climate commitment—the warming that would still occur given no further human influence—is a fundamental metric for both science and policy. It informs us of the minimum climate change we face and, moreover, depends only on our knowledge of the natural climate system. Studies of the climate commitment due to CO2 find that global temperature would remain near current levels, or even decrease slightly, in the millennium following the cessation of emissions. However, this result overlooks the important role of the non‐CO2 greenhouse gases and aerosols. This paper shows that global energetics require an immediate and sig- nificant warming following the cessation of emissions as aerosols are quickly washed from the atmosphere, and the large uncertainty in current aerosol radiative forcing implies a large uncertainty in the climate commitment. Fundamental constraints preclude Earth returning to pre‐industrial temperatures for the indefinite future. These same constraints mean that observations are currently unable to eliminate the possibility that we are already beyond the point where the ultimate warming will exceed dangerous levels. Models produce a narrower range of climate commitment, but under- sample observed forcing constraints.
Impact of reduced Arctic sea ice on Greenland ice sheet variability in a warmer than present climate
A global climate model with interactive vegetation and a coupled ice sheet-shelf component is used to test the response of the Greenland ice sheet (GIS) to increased sea surface temperatures (SSTs) and reduced sea ice (SI) cover during the mid-Pliocene warm period (∼3 Ma) as reconstructed from proxy records. Seasonally open water in the Arctic and North Atlantic are shown to alter regional radiation budgets, storm tracks, and moisture and heat advection into the Greenland interior, with increases in temperature rather than precipitation dominating the ice sheets response. When applied to an initially glaciated Greenland, the presumed warm, ice-free Pliocene ocean conditions induce rapid melting of nearly the entire ice sheet and preclude a modern-like GIS from (re)growing, regardless of orbital forcing. The sensitivity of Greenland to imposed Pliocene ocean conditions may have serious implications for the future response of the ice sheet to continued warming in the Arctic basin.
Observed relation between evapotranspiration and soil moisture in the North American monsoon region
Soil moisture control on evapotranspiration is poorly understood in ecosystems experiencing seasonal greening. In this study, we utilize a set of multi-year observations at four eddy covariance sites along a latitudinal gradient in vegetation greening to infer the ET-q relation during the North American monsoon. Results reveal significant seasonal, interannual and ecosystem variations in the observed ET-q relation directly linked to vegetation greening. In particular, monsoon-dominated ecosystems adjust their ET-q relation, through changes in unstressed ET and plant stress threshold, to cope with differences in water availability. Comparisons of the observed relations to the North American Regional Reanalysis dataset reveal large biases that increase where vegetation greening is more significant. The analysis presented here can be used to guide improvements in land surface model parameterization in water-limited ecosystems.
Declining annual streamflow distributions in the Pacific Northwest United States, 1948–2006
Much of the discussion on climate change and water in the western United States centers on decreased snowpack and earlier spring runoff. Although increasing variability in annual flows has been noted, the nature of those changes is largely unexplored. We tested for trends in the distribution of annual runoff using quantile regression at 43 gages in the Pacific Northwest. Seventy-two percent of the stations showed significant (a = 0.10) declines in the 25th percentile annual flow, with half of the stations exceeding a 29% decline and a maximum decline of 47% between 1948 and 2006. Fewer stations showed statistically significant declines in either median or mean annual flow, and only five had a significant change in the 75th percentile, demonstrating that increases in variance result primarily from a trend of increasing dryness in dry years. The asymmetric trends in streamflow distributions have implications for water management and ecology well beyond those of shifted timing alone, affect both rain and snow-dominated watersheds, and contribute to earlier timing trends in high- elevation watersheds.
Rising temperature depletes soil moisture and exacerbates severe drought conditions across southeast Australia
Over the past decade the southern catchments of the Murray Darling Basin (MDB), responsible for much of Australia’s agricultural output, have experienced a severe drought (termed the ‘‘Big Dry’’) with record high temperatures and record low inflow. We find that during the Big Dry the sensitivity of soil moisture to rainfall decline is over 80% higher than during the World War II drought from 1937 – 1945. A relationship exists between soil moisture and temperature independent of rainfall, particularly in austral spring and summer. Annually, a rise of 1°C leads to a 9% reduction in soil moisture over the southern MDB, contributing to the recent high sensitivity. Since 1950, the impact from rising temperature contributes to 45% of the total soil moisture reduction. In a warming climate, as the same process also leads to an inflow reduction, the reduced water availability can only be mitigated by increased rainfall. Other implications for future climate change are discussed.
Reduction of spring warming over East Asia associated with vegetation feedback
Over East Asia, surface air temperature displays a significant increasing trend particularly in early months of the year for the period of 1982 – 2000. Warming per decade is strongest in late winter, 1.5°C in February and 1.1°C in March, but is significantly reduced in spring, 0.4°C in April and 0.1°C in May. During the analysis period, the reduced temperature increase from late winter to spring is found to be in contrast with the increased vegetation greenness derived from the satellite-measured leaf area index over the domain. We examined this inverse relationship using two climate model experiments— coupled with and without a dynamic vegetation model. In both experiments, strong warming in winter is relatively well reproduced, but weak warming in spring is observed only in the coupled experiment. Analysis of the surface energy budget indicates that weaker spring warming results from an evaporative cooling effect due to the increased vegetation greenness. Over East Asia, the vegetation-evaporation feedback, therefore, may produce seasonal asymmetry in the warming trend.
How natural and anthropogenic influences alter global and regional surface temperatures: 1889 to 2006
To distinguish between simultaneous natural and anthropogenic impacts on surface temperature, regionally as well as globally, we perform a robust multivariate analysis using the best available estimates of each together with the observed surface temperature record from 1889 to 2006. The results enable us to compare, for the first time from observations, the geographical distributions of responses to individual influences consistent with their global impacts. We find a response to solar forcing quite different from that reported in several papers published recently in this journal, and zonally averaged responses to both natural and anthropogenic forcings that differ distinctly from those indicated by the Intergovernmental Panel on Climate Change, whose conclusions depended on model simulations. Anthropogenic warming estimated directly from the historical observations is more pronounced between 45°S and 50°N than at higher latitudes whereas the model-simulated trends have minimum values in the tropics and increase steadily from 30 to 70°N.
Climate effects of global land cover change
When changing from grass and croplands to forest, there are two competing effects of land cover change on climate: an albedo effect which leads to warming and an evapotranspiration effect which tends to produce cooling. It is not clear which effect would dominate. We have performed simulations of global land cover change using the NCAR CAM3 atmospheric general circulation model coupled to a slab ocean model. We find that global replacement of current vegetation by trees would lead to a global mean warming of 1.3°C, nearly 60% of the warming produced under a doubled CO2 concentration, while replacement by grasslands would result in a cooling of 0.4°C. It has been previously shown that boreal forestation can lead to warming; our simulations indicate that mid- latitude forestation also could lead to warming. These results suggest that more research is necessary before forest carbon storage should be deployed as a mitigation strategy for global warming.
High-Resolution Greenland Ice Core Data Show Abrupt Climate Change Happens in Few Years
The last two abrupt warmings at the onset of our present warm interglacial period, interrupted by the Younger Dryas cooling event, were investigated at high temporal resolution from the North Greenland Ice Core Project ice core. The deuterium excess, a proxy of Greenland precipitation moisture source, switched mode within 1 to 3 years over these transitions and initiated a more gradual change (over 50 years) of the Greenland air temperature, as recorded by stable water isotopes. The onsets of both abrupt Greenland warmings were slightly preceded by decreasing Greenland dust deposition, reflecting the wetting of Asian deserts. A northern shift of the Intertropical Convergence Zone could be the trigger of these abrupt shifts of Northern Hemisphere atmospheric circulation, resulting in changes of 2 to 4 kelvin in Greenland moisture source temperature from one year to the next.
Greenhouse Gassed: Carbon Dioxide Spells Indigestion for Food Chains
The author closes with a quote from a biologist who asks who will be chasing wild ungulates with nutrition supplements. CO2 is a fertilizer, with side effects. Plants may grow more rapidly, but at the cost of their nutritional value. Hessman interviews researchers studying this effect on a range of animals from insects to mammals.
GREEN-TREE RETENTION IN HARVEST UNITS: BOON OR BUST FOR BIODIVERSITY?.pdf
etween trees and man there is a rift in the perception of time, and forest managers have no choice but to yield to the pace of the trees. This can make innovations in forest management difficult to evaluate. Nonetheless, innovation is key to meeting society’s changing expectations. It is not just timber anymore. Biodiversity, recreation, aesthetics, and clean water all share top billing with a sustainable crop of timber. And although novel silvicultural strategies are being promoted to meet these complex demands, without the benefit of time, it is difficult to know exactly how well they will achieve their goals.
SOME REFLECTIONS ON CLIMATE CHANGE, GREEN GROWTH ILLUSIONS AND DEVELOPMENT SPACE
Many economists and policy makers advocate a fundamental shift towards “green growth” as the new, qualitatively-different growth paradigm, based on enhanced material/resource/energy efficiency and drastic changes in the energy mix. “Green growth” may work well in creating new growth impulses with reduced environmental load and facilitating related technological and structural change. But can it also mitigate climate change at the required scale (i.e. significant, absolute and permanent decline of GHG emissions at global level) and pace? This paper argues that growth, technological, population-expansion and governance constraints as well as some key systemic issues cast a very long shadow on the “green growth” hopes. One should not deceive oneself into believing that such evolutionary (and often reductionist) approach will be sufficient to cope with the complexities of climate change. It may rather give much false hope and excuses to do nothing really fundamental that can bring about a U-turn of global GHG emissions. The proponents of a resource efficiency revolution and a drastic change in the energy mix need to scrutinize the historical evidence, in particular the arithmetic of economic and population growth. Furthermore, they need to realize that the required transformation goes beyond innovation and structural changes to include democratization of the economy and cultural change. Climate change calls into question the global equality of opportunity for prosperity (i.e. ecological justice and development space) and is thus a huge developmental challenge for the South and a question of life and death for some developing countries (who increasingly resist the framing of climate protection versus equity).
The Influence of Climate, Soils, Weather, and Land Use on Primary Production and Biomass Seasonality in the US Great Plains
Identifying the conditions and mechanisms that control ecosystem processes, such as net primary production, is a central goal of ecosystem ecology. Ideas have ranged from single limiting-resource theories to colimitation by nutrients and climate, to simulation models with edaphic, climatic, and competitive controls. Although some investigators have begun to consider the influence of land-use practices, especially cropping, few studies have quantified the impact of cropping at large scales relative to other known controls over ecosystem processes. We used a 9-year record of produc- tivity, biomass seasonality, climate, weather, soil conditions, and cropping in the US Great Plains to quantify the controls over spatial and temporal patterns of net primary production and to esti- mate sensitivity to specific driving variables. We considered climate, soil conditions, and long-term average cropping as controls over spatial patterns, while weather and interannual cropping varia- tions were used as controls over temporal vari- ability. We found that variation in primary production is primarily spatial, whereas variation in seasonality is more evenly split between spatial and temporal components. Our statistical (multi- ple linear regression) models explained more of the variation in the amount of primary produc- tion than in its seasonality, and more of the spatial than the temporal patterns. Our results indicate that although climate is the most important variable for explaining spatial patterns, cropping explains a substantial amount of the residual variability. Soil texture and depth con- tributed very little to our models of spatial vari- ability. Weather and cropping deviation both made modest contributions to the models of temporal variability. These results suggest that the controls over seasonality and temporal variation are not well understood. Our sensitivity analysis indicates that production is more sensitive to climate than to weather and that it is very sen- sitive to cropping intensity. In addition to iden- tifying potential gaps in out knowledge, these results provide insight into the probable long- and short-term ecosystem response to changes in climate, weather, and cropping. Key words: primary production; carbon; land use; agriculture; climate; weather; soil; seasonality; cropping; grassland; US Great Plains.
