Droughts fires

Drought Fire, depletion of water resources, deterioration of soil, loss of plant and animal life... 

Fire risk Temperature, rainfall, wind, moisture, drought etc. 

The universal spirit] hath a threefold denomination for in respect to its natural heat and fire, it is called Sulphur in respect to its moysture, which is the food and aliment of this fire. Mercury and finally, in respect to the radical drought, which is, as it were, the knot and cement of the fire and moysture, it is called Salt which we shall clear more particularly when we treat hereafter of the three Principles by them-selves. 

Extreme climatic phenomena such as droughts, large shifts of seasonal temperatures, change of solar radiation due to the large-scale input of aerosols to the atmosphere (e.g., by volcanic eruptions or by the large-scale fires that took place in Iraq in connection with recent military operations). 

Natural disasters can be categorized as acute or slow in their onset (Noji, 1996). They are predictable because they cluster in geographic areas. Natural hazards are unpreventable and, for the most part, uncontrollable. Even if quick recovery occurs, natural disasters can have long-term effects. Natural disasters with acute onsets include events such as avalanche blizzard or extreme cold earthquake fire flood heat wave hurricane, cyclone, or typhoon tornado tsunami or storm surge volcanic eruption and wildfire. Natural hazards with a slow or gradual onset include deforestation, desertification, drought, and pest infestation. The most important natural disasters and examples of their environmental effects are listed in Table 17.1. 

During the recent E Nino 1997-98, deficient rainfall in Northern Amazonia, including Iquitos, Peru and the State of Roraima, Brazil, was observed during most of the rainy season. Droughts that lead to forest fires were detected in 1997/98, as it were observed during other very strong ENSO events of 1911/12, 1925/26, 1982/83. 

Fig. 9.4 Soil water content, leaf area, plant water stress, flammability and daily rainfall of mature forest, secondary forest and cattle pasture during the severe 1992 dry season. As deep soil water was depleted during this measurement period (a, b), severe drought stress developed in some trees of the mature forest (d), but the loss of green leaf area was lower in the mature forest than in the secondary forest and cattle pasture (c). Because of this capacity to retain leaves despite severe water stress, the mature forest is rarely susceptible to fire even during a severe dry season such as this (e). Plant-available soil water was measured from 0 to 2 m depth (a) and from 2 to 8 m depth (b) using Time Domain Reflectometry sensors imbedded in the walls of deep soil shafts (Nepstad et al. 1994, Jipp et al. 1998).

However, even in such areas tree roots can penetrate great distances (25-30 ft (lft = 0.3048 m)) below the surface (Nepstad et al., 1994) and reach bedrock (see also Figure 2). If there is a change in the plant cover due to drought, flood, disease, storms, or forest fires, so that the depth of root penetration changes, rate of weathering in low relief areas can change. Also, there... 

Their resilience has a negative side in the face of drought. The leathery leaves of Myrtaceous plants are rich in highly flammable liydrocaibons and present a fire hazard. 

Before the arrival of humanity, the longer-term controls were burial of carbon as carbonate, as methane hydrate in sediment, as gas, as coal, or as reduced organic matter (including charcoal). Before the Devonian, fire would have been impossible, except perhaps on lightning-hit microbial peat bogs after drought. 

Up to 20 grams/m of dust accumulate on glaciers per year. Natural phenomena such as eruptions of volcanoes, earthquakes, mud flows, dust storms, floods, droughts, as well as anthropogenic catastrophes - nuclear tests, fires at petroleum slits, wood cutting and drying of the Aral Sea - exert a huge influence on the pollution of the atmosphere. 

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