Native shellfish populations have dramatically decreased as they are outcompeted by the crabs, causing a decrease in biodiversity.
 
        
             
        
        
        
The factor given in the choices that will probably decrease population density would be C. forest fire. Normal rainfall is beneficial to the ecosystem to help grow the vegetation and in result, benefits the consumers. Predators decrease the population while birth rate can also increase population. 
        
             
        
        
        
The answer would be "Bacilli-<span>Short". </span>
        
             
        
        
        
Deciduous forest
It is a biome dominated by deciduous trees that looses leaves during the winter seasons