Human Population Growth Rates Research Articles

Resource demand estimates for sustainable forest management: Mngazana Mangrove Forest, South Africa

Since democratization in 1994, South African forest policies have promoted sustainable forest management. However, implementation has been problematic due to limited information concerning forest product utilization. This paper investigates and quantifies timber use from the Mngazana Mangrove Forest. Eastern Cape Province. South Africa. Three local communities utilize stems of the mangrove species Rhizophora mucronata Lam. and Bruguiera gymnorrhiza (L.) Lam. for building construction. There were two distinct building shapes, circular and rectangular. On average. 155 stems were used for circular buildings and 378 stems for rectangular buildings. Most buildings were constructed using mangroves as well as indigenous timber from coastal scarp forests. The proportion of mangrove stems in buildings varied from 0 to 95%. The annual demand for mangroves was estimated to be 18 400 stems. Due to the high annual demand, projected human population growth rates have a minor influence upon future demand values. For effective sustainable forest management, the standing stock at Mngazana should be restricted to the two mangrove species utilized for building construction, and a forest inventory performed so that demand for building can be compared to supply.

Accelerated Human Population Growth at Protected Area Edges

Protected areas (PAs) have long been criticized as creations of and for an elite few, where associated costs, but few benefits, are borne by marginalized rural communities. Contrary to predictions of this argument, we found that average human population growth rates on the borders of 306 PAs in 45 countries in Africa and Latin America were nearly double average rural growth, suggesting that PAs attract, rather than repel, human settlement. Higher population growth on PA edges is evident across ecoregions, countries, and continents and is correlated positively with international donor investment in national conservation programs and an index of park-related funding. These findings provide insight on the value of PAs for local people, but also highlight a looming threat to PA effectiveness and biodiversity conservation.

DETERMINANTS OF AGRICULTURAL LAND EXPANSION IN NIGERIA: APPLICATION OF ERROR CORRECTION MODELING (ECM)

This study used an ECM to analyze the determinants of agricultural land expansion in Nigeria. Results show that at first differencing, Augmented Dickey Fuller test indicated stationarity for all the variables (p< 0.05) and there were 7 cointegrating vectors using Johansen test. The dynamic unrestricted short-run parameters of permanent cropland growth rates (68.62), agricultural production index (10.23), livestock population (0.003), human population (-0.145), other land (-0.265) and cereal cropland growth rate (0.621) have significant impact on agricultural land expansion (p< 0.05). The study recommended that appropriate policies to address the problem of expansion of agricultural land and agricultural production must focus on development of cereal and permanent crop hybrids that are high yielding and resistant to environmental stress, human population control and guided use of land for industrial and urban development, among others.

Identifying Sites for Elk Restoration in Arkansas

Abstract: We used spatial data to identify potential areas for elk (Cervus elaphus) restoration in Arkansas. To assess habitat, we used locations of 239 elk groups collected from helicopter surveys in the Buffalo National River area of northwestern Arkansas, USA, from 1992 to 2002. We calculated the Mahalanobis distance (D2) statistic based on the relationship between those elk‐group locations and a suite of 9 landscape variables to evaluate winter habitat in Arkansas. We tested model performance in the Buffalo National River area by comparing the D2 values of pixels representing areas with and without elk pellets along 19 fixed‐width transects surveyed in March 2002. Pixels with elk scat had lower D2 values than pixels in which we found no pellets (logistic regression: Wald χ2 = 24.37, P &lt; 0.001), indicating that habitat characteristics were similar to those selected by the aerially surveyed elk. Our D2 model indicated that the best elk habitat primarily occurred in northern and western Arkansas and was associated with areas of high landscape heterogeneity, heavy forest cover, gently sloping ridge tops and valleys, low human population density, and low road densities. To assess the potential for elk‐human conflicts in Arkansas, we used the analytical hierarchy process to rank the importance of 8 criteria based on expert opinion from biologists involved in elk management. The biologists ranked availability of forage on public lands as having the strongest influence on the potential for elk‐human conflict (33%), followed by human population growth rate (22%) and the amount of private land in row crops (18%). We then applied those rankings in a weighted linear summation to map the relative potential for elk‐human conflict. Finally, we used white‐tailed deer (Odocoileus virginianus) densities to identify areas where success of elk restoration may be hampered due to meningeal worm (Parelaphostrongylus tenuis) transmission. By combining results of the 3 spatial data layers (i.e., habitat model, elk‐human conflict model, deer density), our model indicated that restoration sites located in west‐central and north‐central Arkansas were most favorable for reintroduction.

The story of transgenic cereals: The challenge, the debate, and the solution—A historical perspective

Cereal grains have arguably been the most important source of food and nutrition for humans since the beginning of agriculture nearly 10 000 yr ago. Through much of this time only modest improvements in their quality and yield were attained through natural variation aided by human selection. Significant increases in productivity were made possible only after the rediscovery of Mendel’s laws of heredity at the beginning of the 20th century. These culminated with the exploitation of heterosis and the commercial production of hybrid maize in 1935, followed by the introduction of high-yielding Green Revolution varieties of wheat and rice in the mid-1960s. It is these new varieties that have made cereals the centerpiece of international agriculture, and are widely credited with saving hundreds of millions of human lives, and for spurring economic growth and food sufficiency in many countries, including China and India. Grain production increased 2–3% annually from the mid-1960s to about 1990, staying slightly ahead of the rate of human population growth. Since then annual increases in cereal productivity have declined to about 1%, lower than the rate of population increase. This has become a matter of serious concern for future food security. Many causes are attributed to this plateau in increasing productivity, including adverse soil, water, and environmental factors and the belief that cereals, like most other important food crops, may have reached the physiological limits of their productivity. There has been much discussion and argument, therefore, about finding new and more rapid means to improve crop productivity. Indra K. Vasil – born 1932 ( photo by M. Radlinski).

Disease Risk Assessment in African Great Apes Using Geographic Information Systems

This unique study illustrates the potential application of Geographic Information Systems (GIS) to generate hypotheses regarding which African great ape populations, including bonobos (Pan paniscus), chimpanzees (Pan troglodytes), and gorillas (Gorilla gorilla and Gorilla beringei), are at increased risk from human diseases. Human demographic data and core human health indicator data for the African great ape range countries were obtained. Human population density and percent annual human population growth rate were used as combined indicators of environmental stress/vulnerability (as a proxy measure of human–great ape contact), and infant mortality rate (IMR) and healthy life expectancy (HALE) were used as separate indicators of disease burden among the human populations living in the great ape range countries. Cut-off values were determined and, using GIS, these indicators were analyzed to create maps of critical areas (countries) with both environmental stress and high burden of human diseases. When using IMR as the indicator of disease burden, the great ape range countries identified as critical areas included Benin, Guinea-Bissau, Ivory Coast, Liberia, Nigeria, and Tanzania. Cameroon and Uganda were also identified as critical areas when using HALE as the indicator of disease burden; however, Benin was excluded. Validation of these results would allow for targeted interventions thereby maximizing the use of limited resources. Improvements in public health infrastructure in these critical areas would benefit the human populations that have unmet health needs as well as these endangered species.

Modelling the impacts of group ranch subdivision on agro-pastoral households in Kajiado, Kenya

Pastoral communities in East Africa are facing considerable challenges arising from shifts in land tenure policy from communal to individual landholdings and high human population growth rates. Over the last 30 years, livestock-to-human ratios have generally declined to levels that will no longer support pure pastoralism. Many Maasai have thus diversified into cultivation, wage labour, and small businesses. Livelihood expectations are rising, with concomitant increases in the need for cash. We describe the modification of PHEWS, a simple rule-based model that tracks cash flow and calories in agro-pastoral households. We use it, coupled to Savanna, a sophisticated ecosystem model, to quantify some of the effects of subdivision and land fragmentation on household livestock numbers and on food security. For the group ranches simulated, model outputs indicate that subdivision results in substantial reductions in livestock numbers, partially because households have to sell more animals to generate the cash needed, with serious long-term consequences on herd sizes and food security. If subdivision occurs, even to parcels as large as 196 km 2, livelihood strategies may need to be modified to maintain current levels of household well-being. Model results have been discussed in community meetings in southern Kajiado, but more work is needed on communication mechanisms to utilise more effectively the results of imperfect but useful integrated assessments of complex problems concerning land use and human well-being.

Tsetse control and land-use change in Lambwe valley, south-western Kenya

For a long time, trypanosomosis, spread by the tsetse fly Glossina, constrained human settlement in the Lambwe Valley, a south-western Kenya rangeland. After lengthy efforts to control tsetse over many years, the valley is currently experiencing an increase in human population growth rate, and rapid changes in land-use and cover are taking place. Using time-series aerial photograph interpretation, social survey methods, and a review of human population trends over five decades, a three-fold expansion in cultivation in the settled areas over a 50-year period, with a consequent decrease in woody vegetation cover was identified. In the Ruma National Park, occupying a third of the valley floor, shrublands and thickets have expanded while open grasslands have decreased. The sudden increase of land under cultivation adjacent to prime agricultural land designated for wildlife conservation, exacerbated by bush encroachment and dwindling resources for tsetse control could provide a situation suitable for land-use conflicts. Sustainability of this unique rangeland is dependent on how judiciously the resources are shared among all stakeholders in the valley. This study suggests continued tsetse surveillance and agricultural intensification in the settled areas to minimise chances of conflicts in land-use.

Spatial patterns in species richness and priority areas for conservation of anurans in the Cerrado region, Central Brazil

AbstractDeclines in anuran populations worldwide are increasingly creating demands for quick and urgent strategies to maximize efforts to conserve amphibian populations, especially in areas in which few detailed data on diversity, abundance and distribution are available, such as the Cerrado of Central Brazil. We used extent of occurrence of 105 species of Anura (Amphibia) in the Cerrado region to establish a regional system of potential areas that preserves all anuran species in the region, at a macroecological scale. The final network, obtained using a simple "greedy" algorithm based on complementarity, has a total of 10 regions, widely distributed in the biome. These areas were also evaluated in terms of their human demographic parameters (human population size and growth rate). Strong spatial autocorrelation in species richness indicates that alternative systems based on pre-existing conservation units will also be efficient in terms of biodiversity conservation. Although macro-scale approaches are usually coarse, they can provide overall guidelines for conservation and define the focus for more local and effective conservation efforts, which is particularly important when dealing with a taxonomic group such as anurans for which quick and drastic population declines have been reported in many regions of the world.

Effects of household dynamics on resource consumption and biodiversity.

Human population size and growth rate are often considered important drivers of biodiversity loss, whereas household dynamics are usually neglected. Aggregate demographic statistics may mask substantial changes in the size and number of households, and their effects on biodiversity. Household dynamics influence per capita consumption and thus biodiversity through, for example, consumption of wood for fuel, habitat alteration for home building and associated activities, and greenhouse gas emissions. Here we report that growth in household numbers globally, and particularly in countries with biodiversity hotspots (areas rich in endemic species and threatened by human activities), was more rapid than aggregate population growth between 1985 and 2000. Even when population size declined, the number of households increased substantially. Had the average household size (that is, the number of occupants) remained static, there would have been 155 million fewer households in hotspot countries in 2000. Reduction in average household size alone will add a projected 233 million additional households to hotspot countries during the period 2000-15. Rapid increase in household numbers, often manifested as urban sprawl, and resultant higher per capita resource consumption in smaller households pose serious challenges to biodiversity conservation.

Endemism, diversity, and the threat of tropical moist forest extinctions

Extinction rates have risen to perhaps 10 4 the background rate. Much of this increase is due to projected influences of habitat loss on regions of the world with tropical moist forest. This ecosystem, home to a disproportionate amount of global biodiversity and a major regulator of regional and global climate, also faces disproportionately severe threats. In this study, we collect diversity and endemism data for tropical forested countries of the world, along with areal and socioeconomic data. While a correlation between overall numbers of species and endemic species per country is expected, we demonstrate that endemism patterns among birds and mammals remain very strongly convergent even after statistically rendering all countries equal in size and overall species richness and after adjusting for spatial autocorre- lation. On a per country basis, mammals are generally more threatened than birds in these tropical moist forested countries. Human population growth rates and rising debt among these nations should be viewed as priorities for amelioration by the developed countries. Reserve network extent is not related to numbers of endemic mammals or birds at this large spatial scale.

Long-term changes in Serengeti-Mara wildebeest and land cover: pastoralism, population, or policies?

Declines in habitat and wildlife in semiarid African savannas are widely reported and commonly attributed to agropastoral population growth, livestock impacts, and subsistence cultivation. However, extreme annual and shorter-term variability of rainfall, primary production, vegetation, and populations of grazers make directional trends and causal chains hard to establish in these ecosystems. Here two decades of changes in land cover and wildebeest in the Serengeti-Mara region of East Africa are analyzed in terms of potential drivers (rainfall, human and livestock population growth, socio-economic trends, land tenure, agricultural policies, and markets). The natural experiment research design controls for confounding variables, and our conceptual model and statistical approach integrate natural and social sciences data. The Kenyan part of the ecosystem shows rapid land-cover change and drastic decline for a wide range of wildlife species, but these changes are absent on the Tanzanian side. Temporal climate trends, human population density and growth rates, uptake of small-holder agriculture, and livestock population trends do not differ between the Kenyan and Tanzanian parts of the ecosystem and cannot account for observed changes. Differences in private versus state/communal land tenure, agricultural policy, and market conditions suggest, and spatial correlations confirm, that the major changes in land cover and dominant grazer species numbers are driven primarily by private landowners responding to market opportunities for mechanized agriculture, less by agropastoral population growth, cattle numbers, or small-holder land use.

The Hyperexponential Growth of the Human Population on a Macrohistorical Scale

A qualitative comparison of human population dynamics with some other biological populations growth in free regime is given in this paper along with a quantitative description of human population growth in the last 2000 years. It is shown that human population growth law is very different from the growth laws of other populations: all biological populations grow according to exponential law, whereas the human population grows according to hyperexponential law which essentially moves ahead of the exponential one. It is found that unlike cell populations, the differential equation of rate of human population growth is of second order. This phenomenon can be described due to accelerating function which grows simultaneously with human population number. An analytical hyperexponential equation, which allows to describe dynamics of human population, was obtained.

A Multispecies Overkill Simulation of the End-Pleistocene Megafaunal Mass Extinction

A computer simulation of North American end-Pleistocene human and large herbivore population dynamics correctly predicts the extinction or survival of 32 out of 41 prey species. Slow human population growth rates, random hunting, and low maximum hunting effort are assumed; additional parameters are based on published values. Predictions are close to observed values for overall extinction rates, human population densities, game consumption rates, and the temporal overlap of humans and extinct species. Results are robust to variation in unconstrained parameters. This fully mechanistic model accounts for megafaunal extinction without invoking climate change and secondary ecological effects.

Perceptions and realities of land degradation in arid Otjimbingwe, Namibia

We examined the perceptions and realities of land degradation in a communal ranching area, Otjimbingwe, in arid Namibia (in south-western Africa). It is commonly perceived that large-scale degradation of Otjimbingwe has occurred due to a mixture of improper pastoral practices and pressures induced by a high human population growth rate. We sought to determine whether the inhabitants perceived land degradation to have taken place and whether their perceptions were consistent with empirical data on environmental quality. Furthermore, we wished to determine whether these pastoralists had management strategies to help them withstand the harsh environmental conditions in which they live. All respondents in our surveys perceived that the environment had become degraded. The claimed source of this degradation, a decline in annual rainfall, is inconsistent with long-term rainfall records (there was neither change nor cyclicity in rainfall over time). There is also little evidence of a decline in plant cover and soil quality in spite of the very high stocking densities. No overall pastoral strategy exists in Otjimbingwe. Options for management are extremely limited due to a variety of external and internal pressures such as a high human population growth rate, high immigration into Otjimbingwe, restricted water availability due to dams constructed upstream, and limited movement opportunities for livestock in drought periods.

Green accounting and the welfare gap

Although gross domestic product (GDP) is not intended to be a measure of societal welfare, it is often used as such. One shortcoming as a welfare measure is that it fails to account for the non-marketed value of natural resource flows. The difference between societal welfare and GDP is labelled the ‘welfare gap’. A model that accounts for both market and non-market income flows from natural capital is used to examine this gap. Societal welfare depends on private goods and the stock of natural capital. The latter is subject to a logistic growth relationship common to many non-human species. Private goods are produced using human capital and flows of natural capital. An exogenously growing human population either harvests the natural resource, produces human capital or produces the private good. Optimal control theory and dynamic simulations provide steady-state harvest and human capital growth rates which determine the steady-state natural resource stock, GDP and societal welfare growth rates. The model illustrates the feasibility of explicitly accounting for ecological relationships in economic growth models and shows that, depending on one’s preferences and the growth rate of human population and the intrinsic growth rate of natural resources, GDP may diverge substantially from the growth rate of societal welfare, leaving a large welfare gap.

Distribution, abundance and conservation status of Grauer's gorilla

This report updates the distribution and provides abundance estimates for Grauer's gorilla Gorilla gorilla graueri across its 90,000-sq-km range. The authors divide the range of Grauer's gorilla into four regions within which they identify 11 populations and estimate a total of c. 16,900 individuals. Gorillas found in the Kahuzi-Biega lowland-Kasese region represent 86 per cent of the subspecies's total population. Further, approximately 67 per cent of known Grauer's gorillas inhabit Kahuzi-Biega, Maiko and Virunga National Parks. The eastern region of the Democratic Republic of Congo (formerly Zaire) has an extremely high human population growth rate indicating that deforestation and wildlife use trends will continue to increase. Thus, in spite of the encouraging results of surveys to identify populations and characterize abundance, no Grauer's gorilla population should be considered safe from extirpation.

Distribution, abundance and conservation status of Grauer's gorilla

This report updates the distribution and provides abundance estimates for Grauer's gorilla Gorilla gorilla graueri across its 90,000-sq-km range. The authors divide the range of Grauer's gorilla into four regions within which they identify 11 populations and estimate a total of c. 16,900 individuals. Gorillas found in the Kahuzi-Biega lowland-Kasese region represent 86 per cent of the subspecies's total population. Further, approximately 67 per cent of known Grauer's gorillas inhabit Kahuzi-Biega, Maiko and Virunga National Parks. The eastern region of the Democratic Republic of Congo (formerly Zaire) has an extremely high human population growth rate indicating that deforestation and wildlife use trends will continue to increase. Thus, in spite of the encouraging results of surveys to identify populations and characterize abundance, no Grauer's gorilla population should be considered safe from extirpation.

Optimism About The Environment

Gregg Easterbrook, a journalist who has written about environmental issues in widely read publications such as Newsweek and the New York Times, has now authored a book, A Moment on the Earth: The Coming Age of Environmental Optimism. If you search carefully within this comprehensive survey of environmental issues facing the world today, you can find pockets of common sense and clear thinking. So first, let me give credit where it is due. Easterbrook favors family planning programs that would greatly decrease the rate of human population growth. He supports efforts to increase energy use efficiency, excoriates Detroit for resisting fuel efficiency and emissions reduction standards, and supports a carbon tax. He debunks the notion that environmental protection must lead to economic hardship, stating that no important academic researcher has supported the notion that environmental regulations strangle the economy. He recognizes that private property rights are not absolute in the U.S. and that such right...

Energy content, construction cost and phytomass accumulation of Glycine max (L.) Merr. and Sorghum bicolor (L.) Moench grown in elevated CO2 in the field.

Grain sorghum [Sorghum bicolor (L.) Moench, a C4 crop] and soybean [Glycine max (L.) Merr. cv. Stonewall, a C3 crop] plants were grown in ambient (c. 360μl 1-1 ) and twice-ambient (c. 720 μl 1-1 ) CO2 levels in open-top chambers in soil without root constriction. Plant dry mass, energy content, composition and construction cost (i.e. amount of carbohydrate required to synthesize a unit of plant dry mass) were assessed at the end of the growing season. Elevated CO2 (a) increased phytomass accumulation (kg per plant) in both species, (b) had little affect on energy concentration (MJ kg-1 plant) but caused large increases in the amount of plant energy per ground area (MJ m-2 ground), and (c) did not alter specific growth cost (kg carbohydrate kg-1 plant growth) but greatly increased growth cost per ground area (kg carbohydrate m-2 ground) because growth was enhanced. For soybean, twice-ambient CO2 resulted in a 50 % increase in the amount of nitrogen and energy in grain (seed plus pod) per ground area. This response to elevated CO2 has important implications for agricultural productivity during the next century because the rate of human population growth is exceeding the rate of increase of land used for agriculture so that future food demands can only be met by greater production per ground area.