(a) In some cases, measuring population density by counting individuals may not be feasible. Mention two other parameters that can be used and…

$\displaystyle \star$ Percent cover / biomass, In an area if there are $\displaystyle 200$ carrot grass or Parthenium plants but only single huge banyan tree with a large canopy stating that population density of banyan is low amounts to underestimating the enormous role of Banyan.

$\displaystyle \star$ Relative density, laboratory culture in a petri dish / fish caught per trap

$\displaystyle \star$ Indirect estimate, tiger census in national parks and tiger reserves is often based on pug marks and fecal pellets.

$\displaystyle \star$ Amazonian Rain Forests in South America has remained relatively undisturbed for millions of years.

$\displaystyle \star$ It is less seasonal more constant and predictable.

$\displaystyle \star$ More solar energy available in tropical areas that contributes to higher productivity and more diversity