In order to improve the graph and make it more detailed in order to get a better perception why the honey bee populations are decreasing, there's few things that can be added.
- Number of bee keepers over the period
The number of the honey bee colonies is directly connected as to how many bee keepers there are. If there's a trend of a decline in the bee keepers, than there will be a trend in the decline of the honey bees.
- Area of trees suitable for the honey bees
The trees are crucial for the honey bees to be able to produce honey, thus it is very important that they have a certain area of trees on which they can feed upon. If there's a decline in the number of trees for the bees, than the bees will be dying from starvation.
- Pollution
The honey bees are animals that are very sensitive to changes in the environment, especially when it comes to pollution. If the levels of pollution are increasing in areas where there's honey bees, it will certainly affect their numbers in a negative manner.