Archives par mot-clé : Vegetation

The Proximal Drivers of Large Fires: A Pyrogeographic Study

by Clarke H. et al., April 3, 2020 in FrontierInEarthScience

Variations in global patterns of burning and fire regimes are relatively well measured, however, the degree of influence of the complex suite of biophysical and human drivers of fire remains controversial and incompletely understood. Such an understanding is required in order to support current fire management and to predict the future trajectory of global fire patterns in response to changes in these determinants. In this study we explore and compare the effects of four fundamental controls on fire, namely the production of biomass, its drying, the influence of weather on the spread of fire and sources of ignition. Our study area is southern Australia, where fire is currently limited by either fuel production or fuel dryness. As in most fire-prone environments, the majority of annual burned area is due to a relatively small number of large fires. We train and test an Artificial Neural Network’s ability to predict spatial patterns in the probability of large fires (>1,250 ha) in forests and grasslands as a function of proxies of the four major controls on fire activity. Fuel load is represented by predicted forested biomass and remotely sensed grass biomass, drying is represented by fraction of the time monthly potential evapotranspiration exceeds precipitation, weather is represented by the frequency of severe fire weather conditions and ignitions are represented by the average annual density of reported ignitions. The response of fire to these drivers is often non-linear. Our results suggest that fuel management will have limited capacity to alter future fire occurrence unless it yields landscape-scale changes in fuel amount, and that shifts between, rather than within, vegetation community types may be more important. We also find that increased frequency of severe fire weather could increase the likelihood of large fires in forests but decrease it in grasslands. These results have the potential to support long-term strategic planning and risk assessment by fire management agencies.

Again Reality Goes In Opposite Direction Of Climate Models…”Confidence In Models Correspondingly Low”

by P. Gosselin, March 27, 2019 in NoTricksZone

Real vegetation development in southern Africa takes a very different course than claimed by climate models

By Die kalte Sonne
(German translated by P Gosselin)

Climate models provide answers to all conceivable questions about the future. Political decision-makers are grateful for this information because they can make their plans accordingly.

But are the forecasts derived from models correct at all?

A research team led by Timm Hoffman has now compared the model projections with real vegetation development in southern Africa using historical photos. The sobering result: Nature has mostly developed quite differently than assumed by the models. In contrast to the model assumptions, no significant long-term trend in precipitation could be observed. Vegetation belts, which were supposed to shrink, ended up expanding. Confidence in the models is correspondingly low.

Political planning or even CO2 damage calculations based on the simulations are not possible. Here is the abstract of the work published in the journal Anthropocene in March 2019:

Southern Africa vegetation expanding, images show. Source: here.

The Sahara Is Growing (Even Though It’s Wetter & Greener!)

by P. Homewood, April 1, 2018 in NotaLotofPeopleKnowThat

The green shoots of recovery are showing up on satellite images of regions including the Sahel, a semi-desert zone bordering the Sahara to the south that stretches some 2,400 miles (3,860 kilometers).

Images taken between 1982 and 2002 revealed extensive regreening throughout the Sahel, according to a new study in the journal Biogeosciences.

The study suggests huge increases in vegetation in areas including central Chad and western Sudan.