Biologists explain the higher species richness in tropical regions through the following reasons:
- Stable Climate: Tropical regions have a stable climate over long periods, which supports the survival and evolution of diverse species.
- Higher Solar Energy: These regions receive abundant solar energy, increasing productivity and resource availability, which supports a higher number of species.
- Absence of Severe Climatic Changes: Unlike temperate regions, tropical areas experience minimal climatic disruptions, allowing uninterrupted species evolution.
A biologist surveyed islands of different sizes and consolidated the results in the form of the data given below. Study the data carefully and answer the questions that follow.
Based on data (Birds decline, Plants % decline, Area decline), interpret two reasons for change in the population of migratory birds. 

In an economy, exclusion of _______ may lead to under estimation of the value of Gross Domestic Product (GDP).
