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(Medina 1993). It may much exceed the import via rain (Tables 10.10 and 10.12).

The global role of fires has been surveyed by Fontan (1993). Table 10.13 shows the annual turnover of biomass in forests and savannas in the tropical regions of the world. The contribution of savanna fires to the total biomass burnt per year is seen to be high in America but particularly so in Africa. Fires not only cause losses of minerals but also make a significant contribution to atmospheric loading of infrared-active gases which cause the greenhouse effect (CO2, CO, CH4,03) and with straightforward pollutants (like CO, N-oxides, 03) (Table 10.14).

Frequent man-made fires also open the soil surface to solar radiation, which leads to oxidation and burning of humus (Eiten 1972) and leaching following rainfall. Therefore in dry savannas fire is always detrimental.

Moreover, of course, fire always damages the forests unless it is wet gallery forest with permanently inundated soil (Fig. 10.28). The fires intrude from the edges

Fig. 10.28 Savanna in the Llanos of Venezuela near Puerto Ayacucho with scattered islands of semi-evergreen forest and wet gallery forest (background to the right)
Table 10.13 Burnt biomass in the tropical regions of the world from tropical forests, savannas and other sources (firewood plus agricultural waste) in Tg dry matter per year. (After Fontan 1993)

Tropical region

Forests

Savannas

Other sources

America

590 (34%)

770 (44%)

370 (22%)

Africa

390 (12%)

2430 (76%)

400 (12%)

Asia

280 (13%)

70 (3%)

1840 (84%)

Oceania

- (0%)

420 (94%)

25 (6%)

Total

1260 (17%)

3690 (49%)

2635 (34%)

Table 10.14 Global gas emissions form bushfires in Tg year 1 and in % of total global emissions. (Fontan 1993)

Compound Emissions from bush fires

Table 10.14 Global gas emissions form bushfires in Tg year 1 and in % of total global emissions. (Fontan 1993)

Compound Emissions from bush fires

Carbon dioxide (CO2)

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Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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