Source-sink dynamics

• Source–sink dynamics is a theoretical model used by ecologists to describe how variation in habitat quality may affect the population growth or decline of organisms.
• Since quality is likely to vary among patches of habitat, it is important to consider how a low quality patch might affect a population.
• In this model, organisms occupy two patches of habitat.

1. One patch, the source, is a high quality habitat that on average allows the population to increase.
2. The second patch, the sink, is a very low-quality habitat that, on its own, would not be able to support a population.

• However, if the excess of individuals produced in the source frequently moves to the sink, the sink population can persist indefinitely. Organisms are generally assumed to be able to distinguish between high and low-quality habitat and to prefer high-quality habitats.
• However, the ecological trap theory describes the reasons why organisms may actually prefer sink patches over source patches.
• Finally, the source-sink model implies that some habitat patches may be more important to the long-term survival of the population, and considering the presence of source-sink dynamics will help inform conservation decisions.
• Recently tiger surveys in India has shown the tiger population in the source-sink in the ratio of 60:40. 33% of the tiger population in India lives outside its source i.e, tiger reserves.
• It moves towards the sink due to a decline in the capacities of the tiger reserves to further hold the tiger population. 17/50 tiger reserves in India are going to achieve its maximum capacity to holf the tiger populations.

Ecological traps

• Ecological traps are scenarios in which rapid environmental change leads organisms to prefer to settle in poor-quality habitats.
• The concept stems from the idea that organisms that are actively selecting habitat must rely on environmental cues to help them identify high-quality habitat.
• If either the habitat quality or the cue changes so that one does not reliably indicate the other, organisms may be lured into poor-quality habitat.
• Ecological traps are thought to occur when the attractiveness of a habitat increases disproportionately in relation to its value for survival and reproduction.
• The result is preference of falsely attractive habitat and a general avoidance of high-quality but less-attractive habitats.

Kafala system

• The kafala system is an exploitative system used to monitor migrant labourers, working primarily in the construction and domestic sectors in Gulf Cooperation Council member states and a few neighbouring countries.
• The system requires all unskilled labourers to have an in-country sponsor, usually their employer, who is responsible for their visa and legal status.
• This practice has been criticised by human rights organizations for creating easy opportunities for the exploitation of workers, as many employers take away passports and abuse their workers with little chance of legal repercussions.