TY - JOUR A1 - Franck, Siegfried A1 - von Bloh, Werner A1 - Müller, Christoph A1 - Bondeau, Alberte A1 - Sakschewski, B. T1 - Harvesting the sun new estimations of the maximum population of planet Earth JF - Ecological modelling : international journal on ecological modelling and engineering and systems ecolog N2 - The maximum population, also called Earth's carrying capacity, is the maximum number of people that can live on the food and other resources available on planet Earth. Previous investigations estimated the maximum carrying capacity as large as about 1 trillion people under the assumption that photosynthesis is the limiting process. Here we use a present state-of-the-art dynamic global vegetation model with managed planetary land surface, Lund-Potsdam-Jena managed Land (LPJmL), to calculate the yields of the most productive crops on a global 0.5 degrees x 0.5 degrees grid. Using the 2005 crop distribution the model predicts total harvested calories that are sufficient for the nutrition of 11.4 billion people. We define scenarios where humankind uses the whole land area for agriculture, saves the rain forests and the boreal evergreen forests or cultivates only pasture to feed animals. Every scenario is run in an extreme version with no allowance for urban and recreational needs and in two soft versions with a certain area per person for non-agricultural use. We find that there are natural limits of the maximum carrying capacity which are independent of any increase in agricultural productivity, if non-agricultural land use is accounted for. Using all land planet Earth can sustain 282 billion people. The save-forests-scenario yields 150 billion people. The scenario that cultivates only pasture to feed animals yields 96 billion people. Nevertheless, we should always have in mind that all our calculated numbers for the carrying capacity refer to extreme scenarios where humankind may only vegetate on this planet. Our numbers are considerably higher than the general median estimate of upper bounds of human population found in the literature in the order of 10 billion. KW - Maximum population KW - Human carrying capacity KW - Photosynthesis KW - Dynamical global vegetation model Y1 - 2011 U6 - https://doi.org/10.1016/j.ecolmodel.2011.03.030 SN - 0304-3800 VL - 222 IS - 12 SP - 2019 EP - 2026 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Gerten, Dieter A1 - Hoff, Holger A1 - Bondeau, Alberte A1 - Lucht, Wolfgang A1 - Smith, Pascalle A1 - Zaehle, Sönke T1 - Contemporary "green" water flows : simulations with a dynamic global vegetation and water balance model N2 - "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 similar to 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. (c) 2005 Elsevier Ltd. All rights reserved Y1 - 2005 SN - 1474-7065 ER - TY - JOUR A1 - Cramer, Wolfgang A1 - Bondeau, Alberte A1 - Schaphoff, Sibyll A1 - Lucht, Wolfgang A1 - Smith, Benjamin A1 - Sitch, Stephan T1 - Tropical forests and the global carbon cycle : impacts of atmospheric carbon dioxide, climate change and rate of deforestation N2 - The remaining carbon stocks in wet tropical forests are currently at risk because of anthropogenic deforestation, but also because of the possibility of release driven by climate change. To identify the relative roles of CO2 increase, changing temperature and rainfall, and deforestation in the future, and the magnitude of their impact on atmospheric CO2 concentrations, we have applied a dynamic global vegetation model, using multiple scenarios of tropical deforestation (extrapolated from two estimates of current rates) and multiple scenarios of changing climate (derived from four independent offline general circulation model simulations). Results show that deforestation will probably produce large losses of carbon, despite the uncertainty about the deforestation rates. Some climate models produce additional large fluxes due to increased drought stress caused by rising temperature and decreasing rainfall. One climate model, however, produces an additional carbon sink. Taken together, our estimates of additional carbon emissions during the twenty-first century, for all climate and deforestation scenarios, range from 101 to 367 Gt C, resulting in CO2 concentration increases above background values between 29 and 129 p.p.m. An evaluation of the method indicates that better estimates of tropical carbon sources and sinks require improved assessments of current and future deforestation, and more consistent precipitation scenarios from climate models. Notwithstanding the uncertainties, continued tropical deforestation will most certainly play a very large role in the build-up of future greenhouse gas concentrations Y1 - 2004 SN - 0962-8436 ER -