Human fertility and religions in sub-Saharan Africa: A comprehensive review of publications and data, 2010-2020.

Fertility is declining only slowly in Sub-Saharan Africa (SSA) and religion may be one factor involved. Based on the literature, we reviewed fertility rates of followers of different religions in SSA, and whether religion influences fertility. We used the Web of Science, Scopus, Google Scholar and reference lists to find papers, selected based on inclusion and exclusion criteria. Within 21 countries, followers of African Indigenous Religions (AIR) had higher fertility (4-58%) than Christians. Within 25 countries, followers of Islam had higher fertility (2-36%) than Christians, though not in Zimbabwe and Uganda (-2% in each). Followers of AIR and Islam had on average similar fertility levels, as had Protestants and Catholics. Fertility was associated with religion-related themes in focus-groups and interviews. The most frequent themes for "increasing fertility" were related to religion (11 cases) and polygamy (11), whereas the most frequent themes for "limiting fertility" were financial constraints (7) and quality of life (5). These and other results suggest that religious denominations and faith contribute to high fertility in SSA.

Population growth and climate change: Addressing the overlooked threat multiplier.

Demographic trends will play a role in determining the magnitude of climate disruption and the ability of societies to adapt to it. Yet policy makers largely ignore the potential of fertility changes and population growth when designing policies to limit climate disruption and lessen its impacts. Here we argue that rights-based policy interventions could decrease fertility rates to levels consistent with low population pathways. We review country and global level studies that explore the effects of low population pathways on climate change mitigation and adaptation. We then provide rights-based policy recommendations, such as the expansion of voluntary family planning programs that incorporate elements from successful past programs, and highlight current research gaps. In concert with policies that end fossil fuel use and incentivize sustainable consumption, humane policies that slow population growth should be part of a multifaceted climate response. These policies require attention from scientists, policy analysts and politicians.

Human fertility in relation to education, economy, religion, contraception, and family planning programs.

BACKGROUND: The world population is expected to increase greatly this century, aggravating current problems related to climate, health, food security, biodiversity, energy and other vital resources. Population growth depends strongly on total fertility rate (TFR), but the relative importance of factors that influence fertility needs more study. METHODS: We analyze recent levels of fertility in relation to five factors: education (mean school years for females), economy (Gross Domestic Product, GDP, per capita), religiosity, contraceptive prevalence rate (CPR), and strength of family planning programs. We compare six global regions: E Europe, W Europe and related countries, Latin America and the Caribbean, the Arab States, Sub-Saharan Africa, and Asia. In total, 141 countries are included in the analysis. We estimate the strength of relationships between TFR and the five factors by correlation or regression and present the results graphically. RESULTS: In decreasing order of strength, fertility (TFR) correlates negatively with education, CPR, and GDP per capita, and positively with religiosity. Europe deviates from other regions in several ways, e.g. TFR increases with education and decreases with religiosity in W Europe. TFR decreases with increasing strength of family planning programs in three regions, but only weakly so in a fourth, Sub-Saharan Africa (the two European regions lacked such programs). Most factors correlated with TFR are also correlated with each other. In particular, education correlates positively with GDP per capita but negatively with religiosity, which is also negatively related to contraception and GDP per capita. CONCLUSIONS: These results help identify factors of likely importance for TFR in global regions and countries. More work is needed to establish causality and relative importance of the factors. Our novel quantitative analysis of TFR suggests that religiosity may counteract the ongoing decline of fertility in some regions and countries.

Aging Human Populations: Good for Us, Good for the Earth.

As the nations of the world grapple with the task of creating sustainable societies, ending and in some cases reversing population growth will be necessary to succeed. Yet stable or declining populations are typically reported in the media as a problem, or even a crisis, due to demographic aging. This is misguided, as economic analyses show that the costs connected with aging societies are manageable, while the economic, social, and environmental benefits of smaller populations are substantial. Earth's human-carrying capacity has been exceeded; hence, population growth must end and aging societies are unavoidable. They should be embraced as part of a just and prosperous future for people and the other species with whom we share our planet.

Why Be a Shrub? A Basic Model and Hypotheses for the Adaptive Values of a Common Growth Form.

Shrubs are multi-stemmed short woody plants, more widespread than trees, important in many ecosystems, neglected in ecology compared to herbs and trees, but currently in focus due to their global expansion. We present a novel model based on scaling relationships and four hypotheses to explain the adaptive significance of shrubs, including a review of the literature with a test of one hypothesis. Our model describes advantages for a small shrub compared to a small tree with the same above-ground woody volume, based on larger cross-sectional stem area, larger area of photosynthetic tissue in bark and stem, larger vascular cambium area, larger epidermis (bark) area, and larger area for sprouting, and faster production of twigs and canopy. These components form our Hypothesis 1 that predicts higher growth rate for a small shrub than a small tree. This prediction was supported by available relevant empirical studies (14 publications). Further, a shrub will produce seeds faster than a tree (Hypothesis 2), multiple stems in shrubs insure future survival and growth if one or more stems die (Hypothesis 3), and three structural traits of short shrub stems improve survival compared to tall tree stems (Hypothesis 4)-all hypotheses have some empirical support. Multi-stemmed trees may be distinguished from shrubs by more upright stems, reducing bending moment. Improved understanding of shrubs can clarify their recent expansion on savannas, grasslands, and alpine heaths. More experiments and other empirical studies, followed by more elaborate models, are needed to understand why the shrub growth form is successful in many habitats.

Conservation thinning in secondary forest: negative but mild effect on land molluscs in closed-canopy mixed oak forest in Sweden.

Secondary succession is changing the character of many temperate forests and often leads to closed-canopy stands. In such forests set aside for conservation, habitat management alternatives need to be tested experimentally, but this is rarely done. The Swedish Oak Project compares two often debated alternatives: minimal intervention and non-traditional active management (conservation thinning) on plots of each type replicated at 25 sites. We study responses of several taxa, and here report results for land molluscs. They are considered to be sensitive to more open, drier forest and we predicted a negative effect of the thinning (26% reduction of the basal area; mean value for 25 experimental forests). We sampled molluscs in the litter in ten 20 x 25 cm subplots, and by standardised visual search, in each plot. In total, we recorded 53 species of snails and slugs (24 369 individuals) and the mean species richness in plots was 17. Two seasons after thinning, mean (± SE) species richness had decreased by 1.4 (± 0.9) species in thinning plots, but increased by 0.7 (± 1.0) species in minimal intervention plots, a significant but small change with considerable variation among sites. In matched comparisons with minimal intervention, thinning reduced the overall abundance of molluscs. Most species responded negatively to thinning - but only five of the 53 species were significantly affected, and reproduction seemed to be negatively affected in only one species. An ordination analysis did not reveal any particular change in the species community due to thinning. Thus, the negative effect of conservation thinning on land molluscs was apparently mild - one reason was that many trees, shrubs and other forest structures remained after the treatment. Conservation thinning may be recommended, since other taxa are favoured, but minimal intervention is also a useful form of management for molluscs and saproxylic taxa.

Education and advice contribute to increased density of broadleaved conservation trees, but not saplings, in young forest in Sweden.

The effectiveness of different conservation policies is debated, but the policies are rarely evaluated quantitatively. A voluntary or 'soft' policy based mainly on education provides information about ecosystems and effects of land use, to encourage conservation action. Swedish forestry relies mainly on soft policy, with substantial resources for education and advice to more than 200,000 forest owners, while legal regulation is weak. Increased retention of broadleaved trees at clear-cutting, with environmental benefits in the conifer-dominated forestry, is important in the policy. We used the Swedish National Forest Inventory to analyse this policy for young forests in southern Sweden. Between 1983-1987 and 1998-2002 the policy had no positive effect on saplings (1.3m tall to 4.9 cm dbh) of birch, oak, beech and other species that mostly decreased in density, due to planting of conifers and browsing by ungulates. However, broadleaved conservation trees (>or=15 cm dbh) increased in density, e.g. to about one oak and six birches per ha in young coniferous forest in 1998-2002. The relative increase in density was higher for large (>or=20 cm dbh) than for small trees (15-20 cm dbh). The density of conservation trees was higher on forestland of high than of low productivity. Thus, the soft conservation policy did not influence regeneration of saplings in this type of forestry system, but large broadleaved trees were increasingly saved at 'clear-cuttings'. Advice and educational programmes probably contributed to this result. A continued increase in conservation trees at harvest may require economical support to forest owners.

Predation by sparrowhawks decreases with increased breeding density in a songbird, the great tit.

Predators may regulate prey populations if predation rate increases with prey density. Alternatively, if space-limited (e.g. territorial) predators become 'satiated' when prey exceed a certain density, increased prey abundance may lead to reduced predation rate. These alternatives have been difficult to test experimentally for mobile prey in the wild. We present such a test, manipulating the density of great tits (Parus major) by adding nest boxes in territories of sparrowhawks (Accipiter nisus). Predation rate was measured for young tits after they left the nests. Although the great tit is an important prey, there was no evidence for regulation during the breeding season: the rate of hawk predation declined with increasing density of tits. This result was not confounded by changes in breeding density of alternative prey species (other songbirds). Hawk predation can therefore favour dense breeding in a territorial (solitary) bird, and conspecific attraction and aggregation reported in several territorial species may partly result from predation pressure. This result also has potential implications for conservation work.

Predation by sparrowhawks favours early breeding and small broods in great tits.

The selective pressures determining timing of reproduction and brood or litter size in animals remain to be clarified, despite much research. In several detailed studies of birds, selection for an early start of breeding has been demonstrated. Young born early in the season are often assumed to benefit from long experience, high dominance in flocks and/or early settlement in territories. For forest-breeding great tits (Parus major) in Sweden, predation by sparrowhawks (Accipiter nisus) was lower on fledglings hatched early than on those hatched late in the season. Hawk predation may therefore contribute to the higher success of early breeding great tits. Factors favouring early fledglings were (1) increasing food demands over the season in breeding hawks, and (2) hunting by hawks mainly in non-forest habitats when early tit fledglings left their nests. The proportion of fledglings taken was lower in broods of 2-6 than in broods of 7-12, indicating that predation favours small broods. Fledglings in large broods may be more vulnerable due to (1) a higher level of hunger and begging, and (2) higher provisioning rates by parents, which may reveal sites with fledglings to hawks. Territories of sparrowhawks were used as sample units in the statistical analysis, leading to strong inferences about predation at the landscape level.

Parental quality and egg size affect chick survival in a precocial bird, the lapwing Vanellus vanellus.

Effects of egg size and parental quality on lapwing Vanellus vanellus chick survival were studied in southwestern Sweden over 6 years. Chicks from large eggs were heavier at hatching and survived significantly better than those from small eggs. To control for the confounding effect of parental quality on egg size and chick survival, we performed a cross-fostering experiment during 2 years, exchanging clutches between nests with large and small eggs. In control clutches, chicks from large eggs survived better than those from small eggs, but we found no significant difference in chick survival between exchanged clutches. Thus, egg size did not affect chick survival independently of parental quality. Fledging success increased with parental age and/or experience, and with female body mass. Hence, both egg size and parental quality affect chick survival in the lapwing.