There has always been a fundamental interdependency between migration and the environment, but the reality of climate change adds new complexity to this nexus, while making the need to address it all the more urgent. Both gradual environmental change and slow- or sudden onset natural disasters influence population migration patterns but in different ways. Natural disasters may include geological hazards such as earthquakes or volcanic eruptions. They may also be of an atmospheric or hydrological nature, such as tropical storms or floods, with secondary impacts such as landslides. Some of the latter may be exacerbated by climate change. Any natural disasters may cause affected populations to leave their homes at least temporarily, although return is often feasible in the long run.
Although sudden-onset natural disasters are more likely to result in mass displacement, a larger number of people overall is expected to migrate due to a gradual deterioration of environmental conditions. Slow-onset disasters and gradual environmental degradation, including phenomena such as desertification, reduction of soil fertility, coastal erosion and sea-level rise, which may be associated with climate change, impact existing livelihood patterns and systems of production and may trigger different types of migration.
Migration, especially a mass influx of migrants, can affect the environment in places of destination. In particular, unmanaged urbanization as well as camps and temporary shelters may produce strains on the environment. In places of origin, on the other hand, out-migration may alleviate population and land use pressure, sometimes allowing a degraded local ecosystem to recuperate.
The relationship between environmental and climate change and migration is often complicated by the multifaceted associations with other factors, such as population growth, poverty, governance, human security and conflict. The complexities of the migration–environment nexus call for a comprehensive approach in research, policy and practice.
Environmental migration is a multicausal phenomenon, yet one in which environmental drivers play a significant and increasingly determinative role.
- Near or Far?
Environmental migration may take place internally, regionally or internationally. Most empirical research, however, tends to suggest that internal migration, such as rural-urban migration, or movement across immediate borders between neighbouring countries, is likely to be predominant.
- Temporary or Permanent?
The type of environmentally induced migration – whether long or short distance, long or short term – will vary with the type of environmental event or process and their severity.
In cases of irreversible environmental degradation (for instance due to rises in sea level), resulting migration can require relocation of affected populations either internally or to a third country and may become permanent.
- Forced or Voluntary?
Classifying environmental migration as forced may be relatively uncontroversial in cases of imminent or acute natural disaster. Similarly, we can say that at early and intermediate stages of environmental degradation, for example, migration is more likely to be voluntary and be used by the affected populations as a normal or near normal adaptation strategy to environmental and climate change. For the most part, however, the distinction is not clear-cut. Migration is a multi-causal phenomenon: even in cases where the environment is a predominant driver of migration it is usually compounded by social, economic, political and other factors. Furthermore, the decision to move has to be analysed in the context of viable alternatives, which depend, inter alia, on individual, social and even cultural ability to cope with and adapt to climate shocks and stresses.
Environmentally-induced migration is best understood as a continuum, ranging from clear cases of forced to clear cases of voluntary movement, with a grey zone in between.
- Problem or Solution?
Environmental migration is often portrayed as a failure of adaptation and a worst case scenario. However, while migration can be a manifestation of acute vulnerability, it can also represent a logical and legitimate livelihood diversification and adaptation strategy that has been used for millennia and is likely to be of growing importance in the future. Migration can help reduce risk to lives, livelihoods and ecosystems, contribute to income diversification and enhance overall capacity of households and communities to cope with the adverse effects of environmental and climate change.
Migration is not just a failure of adaptation; it is also one of the possible adaptation strategies to climate and environmental change.
- Leave or Stay?
Climate change will have a differentiated impact, depending on the physical conditions and the adaptive capacities of countries and communities concerned. Least developed countries and countries with particularly susceptible geographies (such as small island states) as well as economically and socially marginalized groups within the affected communities – the poor, the elderly, women and children – are most vulnerable. Migration, however, is a coping strategy not open to everyone as it depends on resources, information and other social and personal factors.
Therefore, it is not necessarily the most vulnerable and the most severely affected by environmental and climatic factors who migrate.
- What are the Estimates?
There are no reliable estimates of climate change induced migration. But it is evident that gradual and sudden environmental changes are already resulting in substantial population movements. The number of storms, droughts and floods has increased threefold over the last 30 years with devastating effects on vulnerable communities, particularly in the developing world. In 2008, 20 million persons have been displaced by extreme weather events, compared to 4.6 million internally displaced by conflict and violence over the same period. Gradual changes in the environment tend to have an even greater impact on the movement of people than extreme events. For instance, over the last thirty years, twice as many people have been affected by droughts as by storms ( 1.6 billion compared with approx 718m).
Future forecasts vary from 25 million to 1 billion environmental migrants by 2050, moving either within their countries or across borders, on a permanent or temporary basis, with 200 million being the most widely cited estimate. This figure equals the current estimate of international migrants worldwide.