The world by latitudes: A global analysis of human population, development level and environment across the northesouth axis over the past half century Matti Kummu * , Olli Varis Water & Development Research Group, Aalto University, Tietotie 1E, 02150 Espoo, Finland Keywords: Demography Development Environment GIS analysis Latitudinal analysis North-south axis Global change abstract Development and environmental issues are commonly analysed by using administrative divisions. In this paper, instead, we analysed how the human population and various economic, social and environmental indicators are distributed across the northesouth axis by using latitudinal approach. This was done because many of the factors forming the natural living conditions of human societies, such as climate, are largely depending on the distance to the equator. The analysis was done with the spatial resolution of five latitudinal degrees while the temporal scale of the study includes the last 50 years. We found that only less than 1/8 of the human population lives south of the equator while around 50% of the population dwell within the area between 20  N and 40  N, where also most of the world’s development and poverty related problems are located. Majority of the economic and social indicators are low on both sides of the equator, but go up with the distance from the equator. For environmental indicators, however, the pattern is more heterogenic and is often correlated with the population density. Most populated latitudes are the scarcest on water, and land in there has been taken to agricultural use more than in other parts of the globe. The latitudinal approach allowed us to see geography based development patterns that might not have been visible with more conventional methods such as cross-country analyses on development. The approach was developed substantially beyond the previous studies. Four development directions of using spatial data-based approaches in development studies were identified. Ó 2010 Elsevier Ltd. All rights reserved. Introduction The world population has more than doubled over the last 50 years (UN, 2009; Klein Goldewijk, Beusen, & Janssen, 2010). At the same time, the volume of the world economy has grown 20 fold (as measured with Gross Domestic Product (GDP) per capita) (World Bank, 2010). Also many social development indicators have shown considerable progress in most locations of the world; for example the global life expectancy at birth has grown from 52.5 to 68.9 years in the past half century (UNDP, 2009b; World Bank, 2010). Apart from that, the number of people living under poverty line keeps growing, and so does the stress for the envi- ronment (World Bank, 2009b; WWF, 2010). For instance the growth of freshwater shortage has been very dramatic in various parts of the globe (Kummu, Ward, De Moel, & Varis, 2010). It is common to investigate the progress and status of the indicators for population, social and economic development, as well as natural resources and the environment on an administrative basis, most importantly by countries or regions. This is typical to the analyses and statistics of United Nations Organizations, devel- opment banks and most other international organizations and actors that produce policy relevant statistics and research (e.g. UN, 2009; UNDP, 2009b; World Bank, 2009b; World Water Assessment Programme, 2009; WWF, 2010). This is an understandable and pragmatic approach because for such reports, national (often government) organizations are the data sources and policy makers. Nations are typically further grouped according to geographic regions, income levels (high, middle, low) etc. (e.g. World Bank, 2009b; WWF, 2010). In this paper, however, we investigate these issues from a merely scientific viewpoint by looking at selected indicators across the northesouth axis by using latitudinal approach, and in particular their evolvement over the past half-century. The lat- itudinal approach was chosen due to the fundamental geographic importance of the distance from the equator to almost any conceivable entity in the nature. For example, the terrestrial temperatures and precipitation patterns are depending strongly on the latitudes (see Fig. 1A) although, naturally, other factors such as altitude, distance to the sea, wind patterns, etc. have much influ- ence, too. Consequently, the climatic zones, such as the Köppen * Corresponding author. Tel.: þ358 9 470 23844; fax: þ358 9 470 23856. E-mail addresses: matti.kummu@iki.fi (M. Kummu), olli.varis@tkk.fi (O. Varis). Contents lists available at ScienceDirect Applied Geography journal homepage: www.elsevier.com/locate/apgeog 0143-6228/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.apgeog.2010.10.009 Applied Geography 31 (2010) 495e507