The Economic Impact of Global Climate Change on Mediterranean Rangeland Ecosystems: A Space-for-Time Approach

Global Climate Change (GCC) can bring about changes in ecosystems and consequently in their services value. Here we show that the urban population in Israel values the green landscape of rangelands in the mesic Mediterranean climate region and is willing to pay for preserving it in light of the expected increasing aridity conditions in this region. Their valuation of the landscape is higher than that of the grazing services these rangelands provide for livestock growers. These results stem form a Time-for-Space approach with which we were able to measure changes in biomass production and rainfall at four experimental sites along an aridity gradient.global climate change, ecosystem, choice modeling, landscape, biomass, Environmental Economics and Policy,

Range Dynamic and Sustainability of Mediterranean Grassland

Mediterranean grasslands are a highly diverse and complex ecological resource of considerable economic and environmental importance. Herbaceous plant production that determines the carrying capacity of these grasslands for beef cattle husbandry is not only influenced by climatic factors, habitat characteristics, soil fertility and depth, but also by the stocking density and the nature of the grazing system (Gutman et al., 1999). The yearly Mediterranean pasture cycle is characterized by a temperate, winter-spring growing season and a hot, dormant, summer-autumn dry season. Consequently, pasture growth dynamics result in extremely low biomass availability at the beginning of the rainy season and abundant biomass at the peak of the growing season (Henkin et al., 1998). This is followed by a sharp reduction in amount and quality of the herbaceous vegetation caused by seed dispersal, desiccation, grazing and weathering during the hot and dry summer. Grazing pressure and the consequently highly variable availability and quality of the pasture vegetation determine the nutritional intake of the grazing animals as well the impacts on the growth dynamics of the pasture. High stocking densities interact with forage biomass production, consequently, the amount of standing biomass in the pasture decreases when stocking density increases above a moderate stocking rate. During maturation and seed development, heavy grazing can reduce the potential for re-growth in the following season while at the beginning of the growth season, heavy grazing can inhibit pasture growth to far below that required for adequate animal nutrition. Deferment of heavy stocking at the beginning of the growing season can prevent the fall of pasture production to a low stable equilibrium (Noy-Meir 1975; Gutman et al., 1999). However, with increasingly heavy stocking, deferment must be severely increased to prevent serious reduction of both the growth of the pasture and the nutrition of the grazing herd. The aim of the current study was to identify the productivity and sustainability of Mediterranean grassland under different stocking densities and timing of the grazing on a predominantly annual Mediterranean pasture. The present analysis is based on a long-term experiment (1994 - 2014)

Response to Comment on “Worldwide evidence of a unimodal relationship between productivity and plant species richness”

Tredennick et al. criticize one of our statistical analyses and emphasize the low explanatory power of models relating productivity to diversity. These criticisms do not detract from our key findings, including evidence consistent with the unimodal constraint relationship predicted by the humped-back model and evidence of scale sensitivities in the form and strength of the relationship

Few multiyear precipitation-reduction experiments find a shift in the productivity-precipitation relationship

Well-defined productivity–precipitation relationships of ecosystems are needed as benchmarks for the validation of land models used for future projections. The productivity–precipitation relationship may be studied in two ways: the spatial approach relates differences in productivity to those in precipitation among sites along a precipitation gradient (the spatial fit, with a steeper slope); the temporal approach relates interannual productivity changes to variation in precipitation within sites (the temporal fits, with flatter slopes). Precipitation–reduction experiments in natural ecosystems represent a complement to the fits, because they can reduce precipitation below the natural range and are thus well suited to study potential effects of climate drying. Here, we analyse the effects of dry treatments in eleven multiyear precipitation–manipulation experiments, focusing on changes in the temporal fit. We expected that structural changes in the dry treatments would occur in some experiments, thereby reducing the intercept of the temporal fit and displacing the productivity–precipitation relationship downward the spatial fit. The majority of experiments (72%) showed that dry treatments did not alter the temporal fit. This implies that current temporal fits are to be preferred over the spatial fit to benchmark land-model projections of productivity under future climate within the precipitation ranges covered by the experiments. Moreover, in two experiments, the intercept of the temporal fit unexpectedly increased due to mechanisms that reduced either water loss or nutrient loss. The expected decrease of the intercept was observed in only one experiment, and only when distinguishing between the late and the early phases of the experiment. This implies that we currently do not know at which precipitation–reduction level or at which experimental duration structural changes will start to alter ecosystem productivity. Our study highlights the need for experiments with multiple, including more extreme, dry treatments, to identify the precipitation boundaries within which the current temporal fits remain valid

Field experiments underestimate aboveground biomass response to drought

Researchers use both experiments and observations to study the impacts of climate change on ecosystems, but results from these contrasting approaches have not been systematically compared for droughts. Using a meta-analysis and accounting for potential confounding factors, we demonstrate that aboveground biomass responded only about half as much to experimentally imposed drought events as to natural droughts. Our findings indicate that experimental results may underestimate climate change impacts and highlight the need to integrate results across approaches