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Session Overview
Session
107RC-regional: Assessing, modelling, and analysing land use and land management impacts on the Earth system - Part C: regional analyses
Time:
Thursday, 25/Apr/2019:
3:15pm - 4:45pm

Session Chair: Karlheinz Erb
Location: UniS-A 003
UniS Building, Auditorium A 003, ground floor, 178 seats + 54 seats on gallery on first floor
Session Topics:
What are the visions for the planetary land system?

Session Abstract

Currently, by far more than half of the Earth’s ice-free land surface are managed by humans for the provision of essential resources and services such as food, fibre, energy, and living space for about 7 billion people. These activities affect key processes of the Earth system, including biogeochemical and biophysical properties of the biosphere, and result in daunting sustainability challenges such as climate change or biodiversity loss. A central prerequisite to overcome these sustainability challenges is an improved understanding of the complex and dynamic interactions between the various Earth system components, as well as the various and ubiquitous influence of human activities.

Many remaining unknowns, however, relate to the extent and degree of human impacts on the natural components of the Earth system. While a relatively robust body of knowledge exists on the effect of land-cover conversions (i.e. the land-use induced change from one land cover type to another, for example deforestation), land-use activities that result in changes that occur within the same land-cover type (denoted “land management”) remain much less analysed. However, well-established insights, e.g. on the effects of fertilization or harvest activities, have been reinforced by recent evidence, suggesting the magnitude of management impacts to be substantial and of global proportion. Thus, omitting land management in assessing the role of land use in the Earth system may result in substantial difficulties to elucidate spatiotemporal dynamics and patterns of crucial Earth System processes. Furthermore, an improved understanding of management impacts on the Earth system is required to exploit the possibly large potentials of land use in mitigating the sustainability challenges while at the same time avoiding massive trade-offs or target conflicts that may reduce or even overturn the benefits of such strategies.

Two interacting impediments are responsible for this at least partial neglect: First, major knowledge gaps exist in our qualitative and quantitative understanding of the biogeochemical and biophysical impacts of land management. Second, substantial data gaps on the magnitude and pattern of various management practices prevail. This session assembles contributions that address these currently prevailing impediments in research from a multitude of disciplinary perspectives and spatio-temporal scales, including Earth System modelling, socioecological accounting or ecological case study research. It presents empirical and conceptual approaches aimed at assessing, modelling and analysing the impacts of land management on various components of the Earth system and will discuss novel approaches and databases. These findings are put into context of land use as a tool to mitigate sustainability challenges such as climate change. A particular focus will be on the trade-offs, but also synergies, that emerge when land-management is employed in such strategies.


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Presentations
Full talk
ID: 591 / 107RC-regional: 1
107R Assessing, modelling, and analysing land use and land management impacts on the Earth system
Keywords: forest degradation, UAV-imagery, Dry Chaco

Tracking forest degradation in the Dry Chaco region using high-resolution UAV-SfM techniques

Beatriz Gobbi1,2, Anton Van Rompaey2, Philipp Gaertner3, Pedro Fernandez3, Dante Loto3, Ignacio Gasparri3, Veerle Vanacker1

1Earth and Life Institute, George Lemaître Center for Earth and Climate Research, Université Catholique Louvain, Louvain-la-Neuve, Belgium; 2Division of Geography and Tourism, KULeuven, Heverlee, Belgium; 3Instituto de Ecología Regional, Universidad Nacional de Tucumán, Tucumán, Argentina

Gradual changes in forest structure, biomass and functioning that are the results of forest degradation are challenging to quantify using traditional, classification-based change detection methods. In contrast to forest conversion or natural disturbances, forest degradation is a gradual process through which the forest’s biomass declines, its species composition and vertical complexity change and the soil physico-chemical properties degrade.

Using the woodlands of the Argentinean Dry Chaco ecosystem as an example, this study aims to explore the potential of UAV-derived optical images to monitor forest degradation as a function of change in forest structure. Selective logging, charcoal production, firewood collection and heavy cattle ranching are abundant in the Dry Chaco, and have a different imprint on the forest structure. Along a gradient of forest disturbance frequency and intensity, we collected UAV-imagery in 50 different forest plots (of 4 ha each) in the Argentinean Dry Chaco. Forest degradation indicators were developed to track observable differences in the horizontal and vertical structure of vegetative elements between forest plots, and allow site-level comparison with well-preserved forests.

Our preliminary data show that structural indicators are able to describe efficiently forest degradation from the forest structure. Areas degraded by selective logging are easily distinguishable with the lowering of the vegetation and the densification of the lower strata. More intense degradation related to charcoal production or heavy cattle ranching are also distinguishable and show a structure characterized by many large vegetation openings in encroached forested areas.



Full talk
ID: 601 / 107RC-regional: 2
107R Assessing, modelling, and analysing land use and land management impacts on the Earth system
Keywords: Fire, pasture, livestock, grazing, Kazakhstan

Grazing patterns are a key determinant of fire occurrence in Kazakhstan

Brett Robert Hankerson1,2, Florian Schierhorn1, Daniel Müller1,2,3

1Leibniz Institute of Agricultural Development in Transition Economies, Germany; 2Humboldt Universität zu Berlin, Germany; 3Integrated Research Institute on Transformations of Human-Environment Systems, Germany

Frequently recurring, large fires are archetypal phenomena in semi-arid steppe zones. However, in the steppes of Kazakhstan the frequency and extent of fires in the 2000s was exceptionally high. To date, it is unclear whether climate conditions or changing land use practices contributed more to the high fire occurrence. We hypothesize that the substantial decrease in livestock grazing demand, a result of the drop in livestock numbers after 1990, was a potential contributor to the high occurrence of fire. A reduction in grazing demand—the amount of energy livestock require from grazing—could lead to an increase in fire occurrence by boosting the fuel load—the amount of biomass on the ground. We tested this hypothesis using the MODIS Burned Area Product for Kazakhstan from 2001 to 2017. We compared statistically the area burned to the annual grazing demand at district (rayon) level—the finest administrative scale at which livestock data are available—to test the importance of grazing dynamics in determining fire occurrence. We found clear evidence of a negative correlation between grazing demand and burnt area. We found the highest correlation between grazing demand and burnt area of the subsequent year. Moreover, we demonstrate that grazing demand better explains the trends in fire occurrence than precipitation and temperature patterns. Our results suggest that increased livestock grazing reduces the prevalence of fire, as well as help to better assess and mitigate fire risk in steppe regions where pastoralism predominates.



Full talk
ID: 880 / 107RC-regional: 3
107R Assessing, modelling, and analysing land use and land management impacts on the Earth system
Keywords: Cerrado, Amazon, tropical agriculture, watershed

Ecological and climatic tradeoffs of agricultural intensification and land management in the Amazon-Cerrado frontier

Marcia Macedo1,2, Divino Silvério2, KathiJo Jankowski3, Paulo Brando1,2, Christopher Neill1, Leonardo Maracahipes2, Ludmila Rattis1,2, Linda Deegan1, Michael Coe1,2

1Woods Hole Research Center; 2Instituto de Pesquisa Ambiental da Amazônia; 3United States Geological Survey

The Amazon-Cerrado region of Brazil is among the most active agricultural frontiers in the world. To date, approximately one-fifth of the Amazon rainforest and half of the Cerrado savanna have been cleared to make way for croplands and pasturelands. The resulting landscape is a complex matrix of land uses, ranging from degraded (low productivity, low input) agro-pastoral systems to intensively managed (high productivity, high input) production systems. The precise mix of land uses and their arrangement in the landscape have profound implications for regional climate and the health of terrestrial and aquatic ecosystems.

On a regional scale, our results indicate that land use transitions from forest physiognomies to cropland or pasture result in substantial reductions in mean annual ET (46% and 39%, respectively) and increases in LST (2.5 °C and 2.3 °C). Transitions from woody savannas to cropland or pasture also reduce mean annual ET (24% and 19%, respectively) and increase LST (2.0 °C and 1.7 °C). At a local scale, these changes are directly reflected in changes to stream flow, fire regimes, forest degradation, and crop productivity. Land management can either exacerbate or mitigate these landscape-scale effects. This presentation will synthesize results from field observations, experimental manipulations (e.g. of fire and nutrient additions); and numerical modeling to examine the ecological tradeoffs associated with land management in the intensifying Amazon-Cerrado agricultural frontier.



Full talk
ID: 423 / 107RC-regional: 4
107R Assessing, modelling, and analysing land use and land management impacts on the Earth system
Keywords: Grassland; grazing; climate change; overgrazing; normalized difference vegetation index; spatial panel model; Mongolia; China.

Grassland greening in the Mongolian Plateau and its determinants

Lijuan Miao1,2, Yanjun Ren3, Zhanli Sun1, Daniel Müller1,4

1Leibniz Institute of Agricultural Development in Transition Economies, Germany; 2Nanjing University of Information Science and Technology, China; 3University of Kiel, Germany; 4Humboldt-Universität zu Berlin, Germany

Empirical insights into the impacts of livestock grazing on grassland biomass are scarce. This is unfortunate because livestock grazing is a dominant land use in many regions, and especially in drylands regions where the availability of grassland resources varies substantially over time and space. We quantify the impacts of land management, in the form of grazing, and of climate variables on grassland greenness across the Mongolian Plateau, with 2.75 million km2 the largest contiguous grassland in Asia that occupies a large part of Mongolia and Inner Mongolia, China. We map the grassland greenness, a proxy for biomass, using normalized difference vegetation indices (NDVI) from the Global Inventory Modeling and Mapping Studies (GIMMS). To quantify the determinants of grassland greenness, we regress NDVI on the density of grazing livestock per grassland, precipitation, and temperature using spatial panel models at the county level and for each year from 1982 to 2015. Results show that most parts of the Mongolian Plateau experienced vegetation greening during the growing season in the recent ten years, especially in the central part of Inner Mongolia and the northern, central, and eastern parts of Mongolia. Higher precipitation was the most important factor for higher NDVI while temperature variation had a small negative effect. Animal density positively influenced NDVI in both Mongolia and Inner Mongolia, although only slightly so. Our insights highlight the dominant effect of climate variability on grassland greenness and challenge the common notion of increasing grassland degradation in the Mongolian Plateau due to the rising grazing pressure. We call for further investigation into this topic to strengthen the understanding of livestock management as a major land use in the global dry areas.



Full talk
ID: 511 / 107RC-regional: 5
107R Assessing, modelling, and analysing land use and land management impacts on the Earth system
Keywords: Pest management impacts, ecotoxicity, environmental efficiency, agricultural systems, LCA

Ecotoxicity in Australian agriculture: Regional hotspots and contribution analysis

Francisco Javier Navarro Garcia1, Brett Anthony Bryan2, Brad Ridoutt1, Michalis Hadjikakou2

1CSIRO, Australia; 2Deakin University, Australia

Most studies on the environmental impacts of agriculture tend to focus on single dimensions, or at best reduced subsets of impacts. Plenty of studies have covered the GHG emissions of production of crop and livestock species, and the focus is starting to shift into looking at more local-level impacts such as water scarcity or biodiversity loss. These types of local-level effects are exceedingly tricky to assess due to the difficulty in obtaining good sample sizes for local-level management practice data, and the need to incorporate the effect of local geography on how point-source emissions are transported. In the case of pesticide use, several studies within the last 3 years have found them to hold large responsibility for freshwater biodiversity loss at regulatory threshold levels. Chemical pollution is a now continental-scale environmental threat. We created a state-of-the-art information retrieval system based on Natural Language Processing to harness management practice data (here focusing on active ingredient use) for 69 crop and 3 livestock commodities. Data on the use of 160 active ingredients was analysed using the USEtox model to quantify ecotoxicity potential (in comparative toxic units). We analysed the contribution of commodity groups to total ecotoxicity potential in Australian agriculture, and used geo-referencing to map the spatial patterns of ecotoxicity in order to identify potential regional hotspots. In terms of ecotoxicity, we found that horticultural crops are significantly more intensive than broadacre crops (except sugar), and that pastures are significantly less intensive than broadacre crops. The intensiveness of winter cereals (e.g. wheat, barley, oats) is quite variable; there may be lessons to be learnt by analysing what separates the least intensive areas from the rest. Incorporating the nutritional composition of commodities offers additional insight into the efficiency of different food sources or even different production systems (e.g. grassfed vs. grainfed ruminant meat).



Full talk
ID: 527 / 107RC-regional: 6
107R Assessing, modelling, and analysing land use and land management impacts on the Earth system
Keywords: agro ecological zone, land management, plantation age, soil organic carbon, tillage system

Response of soil organic carbon stocks and fractions to tillage systems and sugarcane plantation ages in Western Kenya

David Ouma Ojuka1, Benson Muchoge1, Richard Onwonga2

1Kenyatta University, Kenya; 2University of Nairobi

Sugarcane plantation systems can adversely affect soil properties especially total soil organic carbon stocks (TSOCst) and fractions. This study was carried out in Western Kenya sugar zones to determine effects of tillage systems (Tractor and Oxen ploughing), and plantation ages (PA) (continuous mono cropping system, 0-10 years, 10-20 years 20 years and above) on TSOCst and fractions (particulate organic carbon, POC, and the mineral associated organic carbon, MOC) in three different Agro ecological zones (AEZs- Upper Midland (Mumias), Lower midland 1 (SONY) and Lower midland 2 (Chemelil). Consequently their effects on TSOCst were simulated using Rothamsted organic carbon turnover model (Roth C Model). SOM was fractionated into labile (>250 μm) and stable (<53 μm) fractions. Cumulative crop residue was greater with tractor tillage systems (TTS) than with the oxen tillage systems (OTS) in the entire sugar zone expect in Mumias TTS where residues were burnt. In terms of PA high SOCst were recorded in the older farms (>20years) with SONY sugar TTS registering the highest average SOCst (80.20 t C/ha). Mean SOCst and fractions differed significantly between the tillage systems and responded to plantation ages, depth and AEZs (P <0.05). The MOC increased with increasing PA both in TTS and OTS, which was in contrast to POC which generally decreased with increasing PA. The predicted results showed that the rate of SOC stock change was positively higher under TTS in comparison to OTS except where burning occurred in TTS for the modelling period of 2017-2067. These results assert the potential role of sugarcane residue management on enhanced SOC sequestration in sugar cane growing belts, in addition linking Roth C model with measured soil data, can be useful for estimating the potential carbon sequestration resulting from land management impacts for improved/maintenance of soil quality for agricultural sustainability and climate mitigation.



 
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