Total fertility rate | EPFL Graph Search

The total fertility rate (TFR) of a population is the average number of children that would be born to a female over their lifetime if: they were to experience the exact current age-specific fertility rates (ASFRs) through their lifetime they were to live from birth until the end of their reproductive life. It is obtained by summing the single-year age-specific rates at a given time. , the total fertility rate varied widely across the world, from 0.78 in South Korea to 6.73 in Niger. Fertility tends to be correlated with levels of economic development. Historically, developed countries have significantly lower fertility rates, generally correlated with greater wealth, education, urbanization, and other factors. Conversely, in least developed countries, fertility rates tend to be higher. Families desire children for their labor and as caregivers for their parents in old age. Fertility rates are also higher due to the lack of access to contraceptives, stricter adherence to religious beliefs, generally lower levels of female education, and lower rates of female employment. As of 2020, the total fertility rate for the world is 2.3. The global TFR has declined rapidly since the 1960s, and some forecasters like Sanjeev Sanyal argue that the effective global fertility rate will fall below global replacement rate, estimated to be 2.3, in the 2020s. This would stabilize world population sometime during the period 2050–2070. The United Nations predicts that global fertility will continue to decline for the remainder of this century and reach a below-replacement level of 1.8 by 2100, and that world population will peak during the period 2084-2088. Taken together, these projections indicate that the human population will achieve zero growth sometime in the second half of this century. The TFR is not based on the fertility of any real group of women since this would involve waiting until they had completed childbearing. Nor is it based on counting up the total number of children actually born over their lifetime.

Reclamation of low fertility soils using by-products and fast-growing trees

Marc Adami

The world population being increasing, a good energy production management is therefore necessary. Biomass production through short forest rotation by using fast-growing trees appears as a sensible way to limit fossil fuel uses. In Mediterranean regions of south-east Spain, soils present weakened ecosystem with low organic matter and nutrients content which are prone to irremediable degradation processes. The very low fertility of those soils usually makes them unfit to food production and so tree plantation with amendment addition seems to be a possible solution in order to use those soil and improve their qualities. In this study, a low fertility soil was exposed to the addition of two types of amendment (a compost of “Alperujo” and one of biosolid) and to the plantation of two different fast-growing trees (poplars and eucalyptus) during a time period of four months. The soil quality was determined by measuring different selected biochemical (β-glucosidase, phosphatase, dehydrogenase and urease activities), chemical (pH, electrical conductivity, organic matter, phosphate, potassium, water-soluble carbon, N-Kjeldahl, permanganate oxidizable carbon and metal extractible with CaCl2) and plants (nutrients, and trace elements) parameters. No significant differences between the different conditions were found. This was due to the very short time period, the too small doses of compost additions and the very high spatial variability due to the field conditions. It seems however that the composts had a positive effect on the chemical and biochemical parameters in the plots planted with poplars as the results presented systematically higher values for the amended plots than for the control plots (without amendment addition). This was attributed to the fact that all poplars were dead at the time of the study and so the soil was not confronted to any interference by the rhizosphere. Most of the parameters (chemical as well as biochemical) of the soil were improved in the eucalyptus plots compared to the poplar ones. This suggests the stimulation of the nutrient cycles by the tree roots, which improved the conditions for the microorganisms, increasing therefore their metabolic activities. The effect of composts in the eucalyptus plots were therefore clearly less obvious, probably due to the fact that the rhizosphere have had more time (tree planted in July 2011) to influence the soil properties than the compost (added in November 2011). Although both composts contained a non negligible quantity of micronutrients and trace elements, the extractible by CaCl2 0.01M quantities in soil (representing the available quantity for plants) did not present values too high to be toxic for plants and were all in normal ranges. The biomass development of the trees seems to have been improved by the compost of “Alperujo”, but presented a very high spatial variability. The compost of biosolids for its part did not show any difference as compared to the control. Next studies should reveal more significant differences between the plots, the soil having more time to react to the new conditions. It is however recommended to increase the addition doses of composts (double or more) in order to show better their effects

2012

Reclamation of low fertility soils using by-products and fast-growing trees

Marc Adami

2012