Nagarahole National Park in southern India is a forest ecosystem that is important for the conservation of large mammals such as the Asian elephant, Elephas maximus. Conflicts between people and elephants in the area surrounding the national park can threaten conservation work. [Figure 2.1] shows a group of Asian elephants. Several coffee farms (farms where coffee is the crop) are found close to Nagarahole National Park. Asian elephants sometimes leave the national park and enter the coffee farms. Elephants damage crops and trees, and sometimes injure people who work on the farms. December trees, Erythrina subumbrans, are planted on coffee farms to provide shade and are often damaged when elephants enter the farms. Some scientists wanted to investigate the reasons why elephants enter coffee farms close to Nagarahole National Park. 20 coffee farms in an area to the south of Nagarahole National Park were chosen at random. In March 2008, the scientists measured four variables at each coffee farm, as shown in Table 2.1. Table 2.1 variable | how the variable was determined for each coffee farm ---|--- water availability | counting the number of ponds, lakes and water holes visible in satellite images density of December trees | counting the number of December trees in ten circular areas, each with a radius of 10 m grass biomass | drying and measuring the dry mass of all the grass leaves collected in 50 randomly selected areas of 0.25 m² distance from Nagarahole National Park | using GPS to measure the distance between the boundary of Nagarahole National Park and the boundary of the farm Farmers from each coffee farm completed a questionnaire to record when elephants entered the farm. The scientists decided to use Spearman's rank correlation to investigate the relationship between each of the four variables in Table 2.1 and the number of months that elephants entered each coffee farm per year.