The line chart shows the changing population numbers of three different types of wild birds, and then a cumulative number of all wild bird species in the United Kingdom from 1970 to 2004.
The index shows that 1970 is represented by the dotted line at 100, the changes in population figures are therefore given in relation to this. A similarity can be seen in the population figures for all the four categories during the first 7 years, growing slightly by around 10 index point.
However, figures shown in this chart observed dramatically different changes during the following 28 years. While the population of coastal species peaked at 140 index points, fluctuating around this figure slightly from 1991, the population of farmland species plunged to its lowest figure of approximately 53 index points in 1998 and stood at this lowest level until the end of the time period shown in this chart. After fluctuating between 90 and 100 index points before 1990, the population of woodland species remained steady at 90 index points from 1990 to 2004. As for the indication of the population for all species, we can see that this figure fluctuated between 100 and 110 index points throughout the period.
Overall, whilst there was a remarkable rise in the population of coastal species, the opposite trend was true for farmland species. At the same time, the number of woodland species experienced a slight downward trend; however, we can see that the average for all types of wild birds witnessed a marginal increase over this time period.