If an objects volume decreases but the mass stays the same why

Density is defined as d=m/v
i.e. density = mass per unit volume. as seen in this equation, an increase in v with constant m would result in a smaller density

Conservation efforts have been effective in "increasing the number of endangered species, reducing all the negative impacts of human activity, and preserving wildlife habitats".hope my answer has you : ) 

Answer the same molecular formula;