All ecosystems are exposed to gradual changes in climate, nutrient loading, habitat fragmentation or biotic exploitation. Nature is usually assumed to respond to gradual change in a smooth way. However, studies on lakes, coral reefs, oceans, forests and arid lands have shown that smooth change can be interrupted by sudden drastic switches to a contrasting state. Although diverse events can trigger such shifts, recent studies show that a loss of resilience usually paves the way for a switch to an alternative state. This suggests that strategies for sustainable management of such ecosystems should focus on maintaining resilience.

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Catastrophic shifts in ecosystems.

Forest systems cover more than 4.1 x 109 hectares of the Earth9s land area. Globally, forest vegetation and soils contain about 1146 petagrams of carbon, with approximately 37 percent of this carbon in low-latitude forests, 14 percent in mid-latitudes, and 49 percent at high latitudes. Over two-thirds of the carbon in forest ecosystems is contained in soils and associated peat deposits. In 1990, deforestation in the low latitudes emitted 1.6 ± 0.4 petagrams of carbon per year, whereas forest area expansion and growth in mid- and high-latitude forest sequestered 0.7 ± 0.2 petagrams of carbon per year, for a net flux to the atmosphere of 0.9 ± 0.4 petagrams of carbon per year. Slowing deforestation, combined with an increase in forestation and other management measures to improve forest ecosystem productivity, could conserve or sequester significant quantities of carbon. Future forest carbon cycling trends attributable to losses and regrowth associated with global climate and land-use change are uncertain. Model projections and some results suggest that forests could be carbon sinks or sources in the future.

https://science.sciencemag.org/content/sci/263/5144/185.full.pdf

Carbon pools and flux of global forest ecosystems.

Timely and accurate change detection of Earth's surface features is extremely important for understanding relationships and interactions between human and natural phenomena in order to promote better decision making. Remote sensing data are primary sources extensively used for change detection in recent decades. Many change detection techniques have been developed. This paper summarizes and reviews these techniques. Previous literature has shown that image differencing, principal component analysis and post-classification comparison are the most common methods used for change detection. In recent years, spectral mixture analysis, artificial neural networks and integration of geographical information system and remote sensing data have become important techniques for change detection applications. Different change detection algorithms have their own merits and no single approach is optimal and applicable to all cases. In practice, different algorithms are often compared to find the best change detection results for a specific application. Research of change detection techniques is still an active topic and new techniques are needed to effectively use the increasingly diverse and complex remotely sensed data available or projected to be soon available from satellite and airborne sensors. This paper is a comprehensive exploration of all the major change detection approaches implemented as found in the literature.

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Change detection techniques

https://www.owrb.ok.gov/quality/standards/pdf_standards/scenicrivers/Smith,%20Tilman%20and%20Nekola%201999.pdf

Eutrophication: impacts of excess nutrient inputs on freshwater, marine, and terrestrial ecosystems

Urban land-cover change threatens biodiversity and affects ecosystem productivity through loss of habitat, biomass, and carbon storage. However, despite projections that world urban populations will increase to nearly 5 billion by 2030, little is known about future locations, magnitudes, and rates of urban expansion. Here we develop spatially explicit probabilistic forecasts of global urban land-cover change and explore the direct impacts on biodiversity hotspots and tropical carbon biomass. If current trends in population density continue and all areas with high probabilities of urban expansion undergo change, then by 2030, urban land cover will increase by 1.2 million km2, nearly tripling the global urban land area circa 2000. This increase would result in considerable loss of habitats in key biodiversity hotspots, with the highest rates of forecasted urban growth to take place in regions that were relatively undisturbed by urban development in 2000: the Eastern Afromontane, the Guinean Forests of West Africa, and the Western Ghats and Sri Lanka hotspots. Within the pan-tropics, loss in vegetation biomass from areas with high probability of urban expansion is estimated to be 1.38 PgC (0.05 PgC yr−1), equal to ∼5% of emissions from tropical deforestation and land-use change. Although urbanization is often considered a local issue, the aggregate global impacts of projected urban expansion will require significant policy changes to affect future growth trajectories to minimize global biodiversity and vegetation carbon losses.

https://www.pnas.org/content/pnas/109/40/16083.full.pdf

Global forecasts of urban expansion to 2030 and direct impacts on biodiversity and carbon pools

A series of hypotheses is presented about the relation of national energy use to national economic activity (both time series and cross-sectional) which offer a different perspective from standard economics for the assessment of historical and current economic events. The analysis incorporates nearly 100 years of time series data and 3 years of cross-sectional data on 87 sectors of the United States economy. Gross national product, labor productivity, and price levels are all correlated closely with various aspects of energy use, and these correlations are improved when corrections are made for energy quality. A large portion of the apparent increase in U.S. energy efficiency has been due to our ability to expand the relative use of high-quality fuels such as petroleum and electricity, and also to relative shifts in fuel use between sectors of the economy. The concept of energy return on investment is introduced as a major driving force in our economy, and data are provided which show a marked decline in energy return on investment for all our principal fuels in recent decades. Future economic growth will depend largely on the net energy yield of alternative fuel sources, and some standard economic models may need to be modified to account for the biophysical constraints on human economic activity.

https://science.sciencemag.org/content/sci/225/4665/890.full.pdf

Energy and the u.s. Economy: a biophysical perspective.

https://mahb.stanford.edu/wp-content/uploads/2014/03/energy-policy_Hall_Lambert_Balogh_2013.pdf

EROI of different fuels and the implications for society

Inspired by previous studies that have indicated consistent or even well-constrained (relatively low variability) relations among carbon (C), nitrogen (N) and phosphorus (P) in soils, we have endeavored to explore general soil C:N:P ratios in China on a national scale, as well as the changing patterns of these ratios with soil depth, developmental stages and climate; we also attempted to determine if well-constrained C:N:P stoichiometrical ratios exist in China’s soil. Based on an inventory data set of 2,384 soil profiles, our analysis indicated that the mean C:N, C:P and N:P ratios for the entire soil depth (as deep as 250 cm for some soil profiles) in China were 11.9, 61 and 5.2, respectively, showing a C:N:P ratio of ~60:5:1. C:N ratios showed relatively small variation among different climatic zones, soil orders, soil depth and weathering stages, while C:P and N:P ratios showed a high spatial heterogeneity and large variations in different climatic zones, soil orders, soil depth and weathering stages. No well-constrained C:N:P ratios were found for the entire soil depth in China. However, for the 0–10 cm organic-rich soil, which has the most active organism–environment interaction, we found a well-constrained C:N ratio (14.4, molar ratio) and relatively consistent C:P (136) and N:P (9.3) ratios, with a general C:N:P ratio of 134:9:1. Finally, we suggested that soil C:N, C:P and N:P ratios in organic-rich topsoil could be a good indicator of soil nutrient status during soil development.

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Pattern and variation of C:N:P ratios in China’s soils: a synthesis of observational data

Economic production and, more generally, most global societies, are overwhelmingly dependant upon depleting supplies of fossil fuels. There is considerable concern amongst resource scientists, if not most economists, as to whether market signals or cost benefit analysis based on today’s prices are sufficient to guide our decisions about our energy future. These suspicions and concerns were escalated during the oil price increase from 2005 – 2008 and the subsequent but probably related market collapse of 2008. We believe that Energy Return On Investment (EROI) analysis provides a useful approach for examining disadvantages and advantages of different fuels and also offers the possibility to look into the future in ways that markets seem unable to do. The goal of this paper is to review the application of EROI theory to both natural and economic realms, and to assess preliminarily the minimum EROI that a society must attain from its energy exploitation to support continued economic activity and social function. In doing so we calculate herein a basic first attempt at the minimum EROI for current society and some of the consequences when that minimum is approached. The theory of the

/pdf/what-is-the-minimum-eroi-that-a-sustainable-society-must-3tc5d5jojh.pdf

What is the Minimum EROI that a Sustainable Society Must Have

Energy and Economics Characteristics and Magnitude of US Energy Resource Systems Environmental and Human Impacts of Energy Extraction and Use Energy and the Management of Renewable Natural Resources Bibliography Index

Charles A. S. Hall

Papers

Energy and the u.s. Economy: a biophysical perspective.

EROI of different fuels and the implications for society

Pattern and variation of C:N:P ratios in China’s soils: a synthesis of observational data

What is the Minimum EROI that a Sustainable Society Must Have

Energy and Resource Quality: The Ecology of the Economic Process