Very often, it is mixed causes that push people on the road to exile: poverty, conflicts, social and political difficulties, environmental problems, …
It is very difficult to know what was the main cause of the decision to leave. Furthermore, the causes of migration are often intertwined: poverty results from conflicts and political and social crises…
Some are leaving for economic reasons. They are looking for better socio-economic prospects and try to work abroad, or they face extreme poverty in their country and see no other option but to leave. Some work legally, while others do not have a work permit and are active in the informal economy.
Migrants do not leave only for themselves, but also for their family or their community: they send money to their families, thus improving the living conditions of their community. The governments of the countries of origin of migrants are also interested in these remittances, which play a key role in their economy. In Mali, for example, according to a World Bank study, money sent by Malians in France has contributed to the construction of 60% of the infrastructure.
Other migrants are leaving due to political circumstances. They flee from wars, ethnic, religious conflicts, human rights abuses, and other such situations. Some are immediately recognized as refugees, often in neighboring countries. Others become asylum seekers. They are not always allowed to work, but many work illegally.
Still others are victims of trafficking and are forced to migrate without necessarily choosing. The profits from human trafficking are estimated at 10 billion dollars per year.
Some do not migrate happily: these are people who leave in the hope of a better life, to escape conflict, natural disaster or persecution. For these people, migration is painful because it represents an uprooting from their country, their language, their relatives.
For others, migration is done out of a desire to discover the world. This is particularly the case for students who go on a school exchange to another country, and tourists of short or longer duration. This migration of discovery or training is encouraged and valued because it allows the discovery of other cultures and personal enrichment.
But it is a migration that is only accessible to a small number of privileged people, in the North as in the South, who have the financial and administrative means to afford this freedom, yet enshrined in the Universal Declaration of Human Rights. man (DUDH) in its article 13.
Impacts of migration
In Central Africa, the proliferation of Bantu speakers has had an impact on the environment. The introduction of new crops and farming techniques changed the natural landscape. Raising cattle has also displaced wild animal species. Agriculture has improved the ability of Bantu speakers to reproduce and expand. However, the impact of agriculture on the environment is also more pronounced than hunting and gathering.
The animals and plants that people spread and grow throughout the Pacific allow them to survive. However, these actions have also had an impact on the island environment. The introduction of exotic animals and plants and human activities have changed the ecosystem of the islands they choose to live on.
Migrating behavior and migration syndrome.
because Individuals show through Behavior, especially through behavioral characteristics (though not exclusive), natural selection will play a role Immigration. At various organizational levels, behavior Is the most personal concern. Behavior is also observable, although in wild populations with high migration rates In the atmosphere, at night, on or in the ocean, the challenge is huge. In insects, laboratory research uses Wind tunnel (Hardie and Powell 2002) or flight field or Balance (Cooter 1983, Han and Gatehouse 1993) more Feasible and allow experimentation and observation.
Birds can now also be studied in wind tunnels (Pennycuick et al., 1997). Based on groundbreaking research Experiment with aphis (Aphis fabae), he monitors locomotive activity and response to resources during laboratory flight Room, J. S. Kennedy (J. S. Kennedy) proposed The special nature of immigration (Kennedy (Kennedy) 1966 and Dingle 1996) and define it as follows: Lasting and smoothing out the effects of exercise The animal’s own motor or activity ability Board the vehicle. It depends on some temporary Prohibit the station to keep responding, but promote its response Ultimate inhibition and recurrence” (Kennedy 1985, p. 8).
The term “vehicle” refers to transportation in the wind or in water currents. As with many insects, A. fabae’s movements are mostly by the wind, but Kennedy insisted that however, aphids had to actively fly to get into the air stream and stay up. The response to the positions summarizing Kennedy’s experimental discoveries was that at the beginning and during the migration flight in the early stages, the aphids would ignore the environmental cue (young bean leaf) they would normally respond to settling down and starting to feed, but that takes some time flight, they would start to react to it again (even overactive). It is a sophisticated expression of frequency observations made for different taxa from butterflies to African ungulates, this migration movement is characteristically undisturbed (Dingle 1996).
Kennedy emphasized this because the suspension of station maintenance is temporary, maybe repeatedly switched on and off. In this way, a migrant can change between migration and foraging along the route, as in famous migratory bird stops. Further emphasis on how to distinguish between the two types of behavior in Kennedy’s (1985) definition of foraging as “reiterative a locomotor activity that is easily interrupted by an encounter with a resource of one particular type. “
As we have already pointed out, migratory behavior itself relies on lower levels of adaptation, especially physiological and adaptive adaptation. Morphology (Åkesson and Hedenström 2007, Ramenofsky And Wingfield 2007) sometimes cause discrepancies In similar immigration and Non-immigrant species. In addition to responding to prompts to initiate and terminate exercise, migration syndrome also includes endogenous mechanisms that initiate and inhibit exercise. These reactions and the necessary metabolism and hormonal changes Prepare for the immigration journey (Dingle 2006). These ones Traits have been integrated into the life history of the organism; for example, not only eating is inhibited, but maturation and reproduction are also inhibited (Kennedy 1985, Ramenofsky and Wingfield 2007).
Morphological features increase strength and Efficiency, such as increased wing length of migratory birds The streamlined enhancement of insects and fish is also considered part of the syndrome (Dingle 2006, Åkessonand Hedenström 2007). The interesting thing is immigration syndrome It has been repeatedly developed in many taxa. Phylogenetic Research fails to reveal deep ancestral patterns (Piersma et al. 2005); instead, the syndrome seems to be due to Need to serve other environments from existing features, A typical example is flying.
The basis of migration syndrome is genetic complex (Figure 1) contains both genes and genetic structure (van Noordwijk et al., 2006; Pulido, 2007; Roff and Fairbairn, 2007). You can also experiment in the following ways Artificial selection and hybridization test, mainly used for insects (Han nationality) And Gatehouse, 1993, Dingle, 2001) Black Hat Warbler (Sylvia atricapilla; Pulido and Berthold 2003). Such an experiment proves the correlation Between features related to immigration and between Reproduction, both of which show the qualities of adaptation. Other expected characteristics of the syndrome, such as trade-offs And these implied suboptimal adaptations, discussed by Sih and colleagues (2004), Pulido (2007) and Roff And Fairbairn (2007).