Human Land Cover Change Research Articles

Compliance of land cover changes with municipal land use planning: Evidence from the Lisbon metropolitan region (1990–2007)

In the past few decades, urbanisation has become a major phenomenon in European cities, thus representing one of the key human land cover changes with socio-economic and environmental impacts. In the Lisbon metropolitan region it is estimated that 17% of natural and farmland have been transformed into artificial areas. Since the end of 1990s, specific EU guidelines have been issued to contain urban sprawl and preserve agricultural land. Spatial planning in Portugal obviously is integrating these assumptions into the statutory land-use master plans. But what is the performance of this land use planning system regarding land cover evolution itself? Based on the Lisbon metropolitan region (LMR), one of the major areas of urban growth in Portugal, we examine spatio-temporal land cover patterns between 1990 and 2007 by integrating cross-matrix analysis, spatial metrics, and gradient analysis. Additionally, we overlay these land cover dynamics with municipal master plans that regulate land development in order to assess the compliance levels of this land-use regulatory system. Results indicate that: artificial areas are growing by coalescence and/or by scattered development along an urban–rural gradient; agricultural land is reducing and fragmentation is increasing to enlarge peri-urban spaces; there are high levels of conversion of agricultural land into urban land in protected areas, thus showing a lack of compliance to the land use regulatory system visible in the existing gaps between the original land-use assignments of the master plan and the actual developments.

Contemporary “green” water flows: Simulations with a dynamic global vegetation and water balance model

“Green water”—the water stored in the soil and productively used for plant transpiration—is an important quantity particularly in rainfed agriculture (in contrast to “blue water” available in streams and lakes, on which irrigation relies). This study provides preliminary estimates of contemporary (1961–1990) global green water flows (i.e. plant transpiration), using a well-established, process-based dynamic global vegetation and water balance model, LPJ. Transpiration is analysed with respect to differences between a simulation that accounts for human land cover changes and a simulation under conditions of potential natural vegetation. We found that historic land cover change usually reduced the green water flow to the atmosphere, resulting in a global decrease of ∼7% in total. To further explore how the biophysical setting influences the green water flow, we analyse the ratio between soil moisture-limited canopy conductance of carbon and water and energy-controlled potential conductance. This plant physiology-based ratio measures the degree to which actual green water flow falls below the potential flow that would occur when the soil is saturated, thus it represents a measure of the water limitation of terrestrial vegetation. We found that plant water limitation is lowest in the wet tropics and at high latitudes, where soil moisture is high enough to meet the atmospheric demand for transpiration. The present results are preliminary, since irrigation is not yet accounted for, and because the model simulations are compromised primarily by the quality of the input data. A more comprehensive and consistent assessment of global green and blue water flows and limitations using an enhanced LPJ model is identified as a prime task for future studies.

Relative climatic effects of landcover change and elevated carbon dioxide combined with aerosols: A comparison of model results and observations

In this study we examine the possibility that the historical total of human landcover changes have had a comparable effect on climate to that of historical increases in CO2 and aerosols. We compared results from two coupled climate model simulations which investigated transient climate changes produced by observed historical changes of CO2 combined with sulfate aerosol forcing with two other climate model simulations that examined the equilibrium climatic effects of currently observed changes in landcover from its natural state. We found that simulated, near‐surface temperature anomalies due to transient increases in atmospheric CO2 combined with aerosols at the level currently observed are of similar amplitude as simulated temperature anomalies due to the direct and remote (nonlocal) equilibrium effects of historical anthropogenic landcover change in all models. Both effects are of comparable amplitude to observed temperature trends in the past 2 decades, the period of largest global surface warming. These results provide evidence for a confounding influence on surface temperatures and may be an indication that the problem of detection of the radiative warming effect of increased CO2 in the observational record may be more complicated than previously appreciated.