Our purpose

Rapid population growth with high risks but window of opportunity

Africa is the 2nd most populated continent after Asia. It is also the 2nd largest continent (again behind Asia), if we consider North and South America as 2 continents. With the world population passing the 8 billion mark in 2022, the UN estimates that more than half of the increase by 2050 will come from sub-Saharan Africa: the world population will then reach 9.7 billion people with a doubling of the population of sub-Saharan Africa over the period.


The relationship between population growth and sustainable development is complex and multidimensional.

Liu Zhenmin, UN Under-Secretary-General for Economic and Social Affairs.
World population estimates between 1950 and 2022 and projections for 2022-2050
World population estimates between 1950 and 2022 and projections for 2022-2050 Source : ONU, World Population Prospects 2022 : Summary of Results, 2022 page 4

In most African countries, the ratio of the working-age population (25-64) has increased as a result of recent fertility declines. This change in age distribution offers a time-limited opportunity to accelerate economic growth per capita. To maximise the potential benefits of such a demographic configuration, countries need to invest in the development of their human capital by ensuring access to quality health care and education at all ages, and by promoting opportunities for productive employment and decent work. It is therefore imperative for African societies to move towards models that are more respectful of the planet, offer opportunities to each of its citizens, and are supported by strong institutions.

Rapid population growth makes it more difficult to eradicate poverty, combat hunger and malnutrition, and increase the coverage of health and education systems. Conversely, achieving the Sustainable Development Goals (SDGs), particularly those related to health, education and gender equality, will help reduce fertility levels and slow global population growth.

Liu Zhenmin, United Nations Deputy Secretary-General for Economic and Social Affairs.

Several planetary boundaries have already been crossed

Planetary boundaries are a concept proposed by researchers at the Stockholm Resilience Center (Sweden) to determine the limits beyond which the resilience capacities of certain subsystems of the Earth system could be jeopardized. They set a framework beyond which human activity would irreversibly threaten the planet’s habitability. Planetary boundaries can then be defined as “a safe operating space for humanity, based on the intrinsic biophysical processes that regulate the stability of the Earth system”. Although the term Planetary ‘boundary’ is commonly used, some prefer to talk of planetary ‘limit’.

The idea here is not to determine a limit beyond which a system would tip over, but rather to highlight the risks of approaching this point of no return.


The boundary is a zone where there is a significant increase in risk, taking into account uncertainty, the precautionary principle, but also the system’s inertia.

The 9 planetary boundaries thus identified are :

Climate change

Setting a limit on CO2 emissions. A critical threshold that must not be exceeded is the concentration of atmospheric CO2: 350 ppm (parts per million), as opposed to over 413 ppm today.

Biodiversity Erosion

Setting a limit on species extinction. The critical threshold, determined by the annual rate of species extinction that must not be exceeded, is 10 species extinctions per year and per million species, as opposed to more than 100 today.

Ocean Acidification

Setting a limit on the amount of CO2 absorbed by the oceans (which depends on CO2 emissions from the atmosphere). The critical threshold, assessed by the level of aragonite saturation below which it should not fall, is 80% with regard to the pre-industrial era, as opposed to approximatively 84% today.

Disruption of the biogeochemical cycles of nitrogen and phosphorus

Setting limits on the use of fertilisers. The critical thresholds, determined by the quantity of compounds released into nature, are 80 million tonnes per year for nitrogen, compared to over 150 million today, and 11 million tonnes per year for phosphorus, compared to over 22 million today.

Land Use Changes

Setting a limit to deforestation. The critical threshold, measured by the percentage of forest area preserved in regards to the original forest cover (before 1700) below which it should not fall, is 75% compared to about 62% today.

Atmospheric Aerosol Loading

No limit value has yet been established. Due to the complexity of aerosols and the spatial and temporal variability of particles, no study can provide a conclusive assessment of the atmospheric aerosol load.

Stratospheric ozone depletion

Setting an emission limit for CFC-type fluorinated gases. The critical threshold, determined by the level of ozone concentration in the atmosphere (measured in Dobson Units ~ DU) below which it should not fall, is 275 DU – that is 95% of pre-industrial level – compared to about 285 DU today

Chemical pollution (or “new entities” created or introduced by man into the biosphere)

For which no limit value has yet been set. These include plastics, pesticides, paints, antibiotics, medicines, heavy metals, radioactive compounds, endocrine disruptors, etc. The production of chemicals has increased more than 50-fold since the early 1950s and could triple by 2050. The critical threshold linked to this limit would already be exceeded ( pubs.acs.org )

Disruption of the freshwater cycle

Setting a limit on surface and groundwater withdrawals. The critical threshold, determined by the maximum volume of freshwater withdrawn from surface and groundwater that must not be exceeded, is 4000 km3 per year, compared with 2600 km3 today. This threshold, which depends locally on the capacity of the environment to respond to these pressures, has already been exceeded in several places around the world, according to numerous researchers ( nature.com )

By 2021, 4 global limits had been crossed. In 2022, 2 new ones were added to the list, which now has 6 global limits reached. The only ones that have not yet been exceeded are: ocean acidification, stratospheric ozone depletion and atmospheric aerosol load (for which quantification remains complex).

Finally, it is essential to emphasise the systemic aspect of the subject of global limits. Indeed, several regulatory processes interact and the disruption of some affects the resilience and/or regulation of others. For example, changes in land use have direct consequences on CO2 concentration. This impacts, on the one hand, the acidification of the oceans, and on the other hand, climate change, which in turn affects the water cycle, biodiversity, and so on. The infographic below shows these interactions.

Global limits and their overshoot, Stockholm Resilience Centre, 2022. The dotted circle represents the estimated sustainability limits and the coloured areas the estimated status in 2022, with orange representing overshoot.
Global limits and their overshoot, Stockholm Resilience Centre, 2022. The dotted circle represents the estimated sustainability limits and the coloured areas the estimated status in 2022, with orange representing overshoot. stockholmresilience.org
An overview of planetary limits, Ex naturae, October 2020
An overview of planetary boundaries, Ex naturae, October 2020. exnaturae.ong

Key issues for Africa

Africa contributed nearly 7% of the historical total of net global carbon dioxide (CO2) emissions between 1850 and 2019 (fig). In 2019 alone, the continent accounts for almost 9% of global net greenhouse gas emissions (up from 7% in 1990). This is not much compared to other regions, but it is already 9% too much in a world that aims to be carbon neutral by 2050.

Historical net CO2 emissions by region, cumulative 1850-2019 Source: IPCC (AR6, WG3, 2022)
Historical net CO2 emissions by region, cumulative 1850-2019 Source: IPCC (AR6, WG3, 2022) Source : GIEC (AR6, GT3, 2022)
Net anthropogenic greenhouse gas emissions by region between 1990 and 2019

Source: IPCC (AR6, WG3, 2022)
Net anthropogenic greenhouse gas emissions by region between 1990 and 2019 Source: IPCC (AR6, WG3, 2022)

In detail, most of the continent’s contribution to historical CO2 emissions is due to land use change, accounting for 75% of the total. The main challenge for African regions with carbon sinks (forests, peatlands, savannahs) is to ensure sustainable management of these ecosystems in order to increase carbon storage and thus contribute to the continent’s carbon neutrality objective while preserving ecosystems and biodiversity.

For many African countries, it is also essential to progressively limit the use of fossil fuels and to massively develop renewable energies, given the continent’s impressive solar, wind and water potential.

Similarly, waste management is an increasingly worrying issue for all the continent’s cities. Very often ranked among the main sources of greenhouse gas emissions in African countries, this sector is the source of major environmental pressures, particularly for marine ecosystems, which are increasingly exposed to plastic pollution.

The Need for a Fair and Sustainable Transition

The environmental issues outlined above must not overshadow all other societal issues, which are no less important from the viewpoint of the fair and sustainable transition that we are all advocating.

Greenhouse gas emissions are only one part of the immense systemic challenges that must lead us to change our lifestyles and consumption patterns. These changes imply a new approach to several concepts whose historical approach is now obsolete: the economy, well-being, equality, etc. The arbitration criteria must no longer be solely environmental (energy production, waste management, water use, etc.), but also societal (equal pay, well-being of populations, job creation, schooling of young people, etc.). A successful transition is one that respects the planetary limits without leaving anyone behind.

The “Carbon” vision tunnel, credit: Jan Konietzko. https://globalreportinginitiative.medium.com