Net Land Use Research Articles

Green buffer areas and green roofs: performance design to improve the urban water cycle

Abstract While in all Europe the land use does not decrease – contrary to EU soil strategy that would actualize the zero net land use by 2050 – cities are plagued by problems such as air pollution, urban heat island effect and uncontrolled run-off following intense rain events, which degrade the environment threatening the health and the safety of inhabitants. The impermeable materials and are responsible for the worsening of the urban water cycle and, at the same time, for the increase in summer air temperatures: both those effects can be mitigated by nature-based and draining solutions. The paper explains the hydrological phenomena of the urban impervious surfaces, highlighting the typical functional defects, providing then a list of various green technologies suitable to overcome the common issues of city centers like high density / reduced spaces, irreversible impervious surfaces, undersized drainage, presence of sub-structures / sub-systems, conservation of architectural heritage. The technical green solutions on the ground (bio-retention systems, rain gardens, trees, pervious pavements…) and on the roofs, specifically designed, behave 1) as a buffer for the stormwater and superficial run-off, being able to collect water, 2) as providers of side effects that can affect water quality, biodiversity, amenity in cities. Experimental results from a rain simulation are presented in order to argue potentials and limitations of these solutions, often narrated as salvific, or, on the contrary, underestimated in their technological specificities.

Global land use implications of dietary trends.

Global food security and agricultural land management represent two urgent and intimately related challenges that humans must face. We quantify the changes in the global agricultural land footprint if the world were to adhere to the dietary guidelines put forth by the United States Department of Agriculture (USDA), while accounting for the land use change incurred by import/export required to meet those guidelines. We analyze data at country, continental, and global levels. USDA guidelines are viewed as an improvement on the current land-intensive diet of the average American, but despite this our results show that global adherence to the guidelines would require 1 gigahectare of additional land—roughly the size of Canada—under current agricultural practice. The results also show a strong divide between Eastern and Western hemispheres, with many Western hemisphere countries showing net land sparing under a USDA guideline diet, while many Eastern hemisphere countries show net land use increase under a USDA guideline diet. We conclude that national dietary guidelines should be developed using not just health but also global land use and equity as criteria. Because global lands are a limited resource, national dietary guidelines also need to be coordinated internationally, in much the same way greenhouse gas emissions are increasingly coordinated.

Quantifying gross vs. net agricultural land use change in Great Britain using the Integrated Administration and Control System

Land use change has impacts upon many natural processes, and is one of the key measures of anthropogenic disturbance on ecosystems. Agricultural land covers 70% of Great Britain's (GB) land surface and annually undergoes disturbance and change through farming practices such as crop rotation, ploughing and the planting and subsequent logging of forestry. It is important to quantify how much of GB's agricultural land undergoes such changes and what those changes are at an annual temporal resolution. Integrated Administration and Control System (IACS) data give annual snapshots of agricultural land use at the field level, allowing for high resolution spatiotemporal land use change studies at the national scale. Crucially, not only do the data allow for simple net change studies (total area change of a land use, in a specific areal unit) but also for gross change calculations (summation of all changes to and from a land use), meaning that both gains and losses to and from each land use category can be defined. In this study we analysed IACS data for GB from 2005 to 2013, and quantified gross change for over 90% of the agricultural area in GB for the first time. It was found that gross change totalled 63,500 km2 in GB compared to 20,600 km2 of net change, i.e. the real year-on-year change is, on average, three times larger than net change. This detailed information on nature of land use change allows for increased accuracy in modelling the impact of land use change on ecosystem processes and is directly applicable across EU member states, where collection of such survey data is a requirement. The modelled carbon flux associated with gross land use change was at times >100 Gg C y−1 larger than that based on net land use change for some land use transitions.

Representing anthropogenic gross land use change, wood harvest, and forest age dynamics in a global vegetation model ORCHIDEE-MICT v8.4.2

Abstract. Land use change (LUC) is among the main anthropogenic disturbances in the global carbon cycle. Here we present the model developments in a global dynamic vegetation model ORCHIDEE-MICT v8.4.2 for a more realistic representation of LUC processes. First, we included gross land use change (primarily shifting cultivation) and forest wood harvest in addition to net land use change. Second, we included sub-grid evenly aged land cohorts to represent secondary forests and to keep track of the transient stage of agricultural lands since LUC. Combination of these two features allows the simulation of shifting cultivation with a rotation length involving mainly secondary forests instead of primary ones. Furthermore, a set of decision rules regarding the land cohorts to be targeted in different LUC processes have been implemented. Idealized site-scale simulation has been performed for miombo woodlands in southern Africa assuming an annual land turnover rate of 5 % grid cell area between forest and cropland. The result shows that the model can correctly represent forest recovery and cohort aging arising from agricultural abandonment. Such a land turnover process, even though without a net change in land cover, yields carbon emissions largely due to the imbalance between the fast release from forest clearing and the slow uptake from agricultural abandonment. The simulation with sub-grid land cohorts gives lower emissions than without, mainly because the cleared secondary forests have a lower biomass carbon stock than the mature forests that are otherwise cleared when sub-grid land cohorts are not considered. Over the region of southern Africa, the model is able to account for changes in different forest cohort areas along with the historical changes in different LUC activities, including regrowth of old forests when LUC area decreases. Our developments provide possibilities to account for continental or global forest demographic change resulting from past anthropogenic and natural disturbances.

Biofuels and Their Co-Products as Livestock Feed: Global Economic and Environmental Implications.

This review studies biofuel expansion in terms of competition between conventional and advanced biofuels based on bioenergy potential. Production of advanced biofuels is generally more expensive than current biofuels because products are not yet cost competitive. What is overlooked in the discussion about biofuel is the contribution the industry makes to the global animal feed supply and land use for cultivation of feedstocks. The global ethanol industry produces 44 million metric tonnes of high-quality feed, however, the co-products of biodiesel production have a moderate impact on the feed market contributing to just 8–9 million tonnes of protein meal output a year. By economically displacing traditional feed ingredients co-products from biofuel production are an important and valuable component of the biofuels sector and the global feed market. The return of co-products to the feed market has agricultural land use (and GHG emissions) implications as well. The use of co-products generated from grains and oilseeds can reduce net land use by 11% to 40%. The proportion of global cropland used for biofuels is currently some 2% (30–35 million hectares). By adding co-products substituted for grains and oilseeds the land required for cultivation of feedstocks declines to 1.5% of the global crop area.

Exposure to low pH induces molecular level changes in the marine worm, Platynereis dumerilii

Fossil fuel emissions and changes in net land use lead to an increase in atmospheric CO2 concentration and a subsequent decrease of ocean pH. Noticeable effects on organisms' calcification rate, shell structure and energy metabolism have been reported in the literature. To date, little is known about the molecular mechanisms altered under low pH exposure, especially in non-calcifying organisms. We used a suppression subtractive hybridisation (SSH) approach to characterise differentially expressed genes isolated from Platynereis dumerilii, a non-calcifying marine polychaeta species, kept at normal and low pH conditions. Several gene sequences have been identified as differentially regulated. These are involved in processes previously considered as indicators of environment change, such as energy metabolism (NADH dehydrogenase, 2-oxoglutarate dehydrogenase, cytochrome c oxidase and ATP synthase subunit F), while others are involved in cytoskeleton function (paramyosin and calponin) and immune defence (fucolectin-1 and paneth cell-specific alpha-defensin) processes. This is the first study of differential gene expression in a non-calcifying, marine polychaete exposed to low pH seawater conditions and suggests that mechanisms of impact may include additional pathways not previously identified as impacted by low pH in other species.

Complex forest dynamics indicate potential for slowing carbon accumulation in the southeastern United States

Over the past century forest regrowth in Europe and North America expanded forest carbon (C) sinks and offset C emissions but future C accumulation is uncertain. Policy makers need insights into forest C dynamics as they anticipate emissions futures and goals. We used land use and forest inventory data to estimate how forest C dynamics have changed in the southeastern United States and attribute changes to land use, management, and disturbance causes. From 2007-2012, forests yielded a net sink of C because of net land use change (+6.48 Tg C yr−1) and net biomass accumulation (+75.4 Tg C yr−1). Forests disturbed by weather, insect/disease, and fire show dampened yet positive forest C changes (+1.56, +1.4, +5.48 Tg C yr−1, respectively). Forest cutting caused net decreases in C (−76.7 Tg C yr−1) but was offset by forest growth (+143.77 Tg C yr−1). Forest growth rates depend on age or stage of development and projected C stock changes indicate a gradual slowing of carbon accumulation with anticipated forest aging (a reduction of 9.5% over the next five years). Additionally, small shifts in land use transitions consistent with economic futures resulted in a 40.6% decrease in C accumulation.

Land use changes from EU biofuel use: a sensitivity analysis

This paper employs the general equilibrium model MAGNET to assess the effects of the European Commission’s proposals for the revision of the Renewable Energy Directive (RED) on land use changes in the European Union and worldwide. The focus of the paper is to evaluate the sensitivity of the land use changes to different assumptions on the blending mix between ethanol and biodiesel for meeting the 5 % blending target of first generation biofuels, on the intensification level of agricultural production and on the available agricultural land. The results suggest that net land use changes (LUC) in the EU due to the revised RED are limited and are more sensitive to the share of ethanol and biodiesel in meeting the blending target compared to different assumptions on the availability of land and of yields that can be achieved when substituting land with other production factors. LUC in the rest of the world stem from increased EU imports of feedstock and of biofuels. LUC is especially sensitive to the substitution between land and fertilizer in regions with extensive agricultural production systems. In regions trading vegetable oil and oilseeds with the EU, and in regions producing ethanol, LUC is influenced by the share of ethanol in the biofuel mix used in the EU.

Terminology as a key uncertainty in net land use and land cover change carbon flux estimates

Abstract. Reasons for the large uncertainty in land use and land cover change (LULCC) emissions go beyond recognized issues related to the available data on land cover change and the fact that model simulations rely on a simplified and incomplete description of the complexity of biological and LULCC processes. The large range across published LULCC emission estimates is also fundamentally driven by the fact that the net LULCC flux is defined and calculated in different ways across models. We introduce a conceptual framework that allows us to compare the different types of models and simulation setups used to derive land use fluxes. We find that published studies are based on at least nine different definitions of the net LULCC flux. Many multi-model syntheses lack a clear agreement on definition. Our analysis reveals three key processes that are accounted for in different ways: the land use feedback, the loss of additional sink capacity, and legacy (regrowth and decomposition) fluxes. We show that these terminological differences, alone, explain differences between published net LULCC flux estimates that are of the same order as the published estimates themselves. This has consequences for quantifications of the residual terrestrial sink: the spread in estimates caused by terminological differences is conveyed to those of the residual sink. Furthermore, the application of inconsistent definitions of net LULCC flux and residual sink has led to double-counting of fluxes in the past. While the decision to use a specific definition of the net LULCC flux will depend on the scientific application and potential political considerations, our analysis shows that the uncertainty of the net LULCC flux can be substantially reduced when the existing terminological confusion is resolved.

Fragmentation in the Legal Amazon, Brazil: Can landscape metrics indicate agricultural policy differences?

Large-scale land conversion for agriculture in Brazilian Amazonia is occurring at persistently high rates. Basin-wide net land use and land cover changes imply substantially different situations between distinct regions and states due to different agricultural policies. This research used eight landscape metrics to quantify and investigate the spatial patterns of cattle pasture and cropland throughout the states of Pará, Mato Grosso, Rondônia, and Amazonas. These metrics were patch density (DEN), mean patch size (MPS), largest patch index (LPI), mean edge density (MED), mean twist number (TWI), corrected perimeter-to-area ratio (CPA), fractal dimension (FDI), and fragmentation index (FRG). A total of 1852 patches were analyzed, originating from 86 samples in 71 different plots, covering a total of 177,500 km 2 throughout all four states. Principal component analysis showed a partial overlap in the spatial pattern of agricultural patches between all states. The largest percentage of variance was explained by patch area metrics, which can be related to the different approaches in agricultural policies, but no clear division between the states was identified in this dimension. The metrics quantifying patch shape were de facto independent of deforestation area, and related to the second principal component axis. Although some overlap in this dimension was present as well, these metrics proved a possible measure for discerning the patterns of agriculture attached to a certain state. Different land use policies are hypothesized to lead to more heterogeneity in landscape patterns in an early stage, yet the increasing influence of both cropland and pasture agriculture eventually leads to more uniform landscapes in which spatial differences gradually disappear.

Contributions of secondary forest and nitrogen dynamics to terrestrial carbon uptake

Abstract. We use a terrestrial carbon-nitrogen cycle component of the Integrated Science Assessment Model (ISAM) to investigate the impacts of nitrogen dynamics on regrowing secondary forests over the 20th century. We further examine what the impacts of nitrogen deposition and land use change history are on terrestrial carbon uptake since preindustrial time. Our results suggest that global total net land use emissions for the 1990s associated with changes in cropland, pastureland, and wood harvest are 1.22 GtC/yr. Without considering the secondary forest regrowth, the estimated net global total land use emissions are 1.58 GtC/yr or about 0.36 GtC/yr higher than if secondary forest regrowth is considered. Results also show that without considering the nitrogen dynamics and deposition, the estimated global total secondary forest sink for the 1990s is 0.90 GtC/yr or about 0.54 GtC/yr higher than estimates that include the impacts of nitrogen dynamics and deposition. Nitrogen deposition alone is responsible for about 0.13 GtC/yr of the total secondary forest sink. While nitrogen is not a limiting nutrient in the intact primary forests in tropical regions, our study suggests that nitrogen becomes a limiting nutrient for regrowing secondary forests of the tropical regions, in particular Latin America and Tropical Africa. This is because land use change activities, especially wood harvest, removes large amounts of nitrogen from the system when slash is burnt or wood is removed for harvest. However, our model results show that carbon uptake is enhanced in the tropical secondary forests of the Indian region. We argue that this may be due to enhanced nitrogen mineralization and increased nitrogen availability following land use change in the Indian tropical forest ecosystems. Results also demonstrate that there is a significant amount of carbon accumulating in the Northern Hemisphere where most land use changes and forest regrowth has occurred in recent decades. This study indicates the significance of secondary forests to terrestrial carbon sinks, the importance of nitrogen dynamics to the magnitude of secondary forests carbon uptake, and therefore the need to include both primary and secondary forests and nitrogen dynamics in terrestrial ecosystem models.

Land Use Change Effects on Forest Carbon Cycling Throughout the Southern United States

We modeled the effects of afforestation and deforestation on carbon cycling in forest floor and soil from 1900 to 2050 throughout 13 states in the southern United States. The model uses historical data on gross (two-way) transitions between forest, pasture, plowed agriculture, and urban lands along with equations describing changes in carbon over many decades for each type of land use change. Use of gross rather than net land use transition data is important because afforestation causes a gradual gain in carbon stocks for many decades, while deforestation causes a much more rapid loss in carbon stocks. In the South-Central region (Texas to Kentucky) land use changes caused a net emission of carbon before the 1980s, followed by a net sequestration of carbon subsequently. In the Southeast region (Florida to Virginia), there was net emission of carbon until the 1940s, again followed by net sequestration of carbon. These results could improve greenhouse gas inventories produced to meet reporting requirements under the United Nations Framework Convention on Climate Change. Specifically, from 1990 to 2004 for the entire 13-state study area, afforestation caused sequestration of 88 Tg C, and deforestation caused emission of 49 Tg C. However, the net effect of land use change on carbon stocks in soil and forest floor from 1990 to 2004 was about sixfold smaller than the net change in carbon stocks in trees on all forestland. Thus land use change effects and forest carbon cycling during this period are dominated by changes in tree carbon stocks.