Graphic literacy is important to understanding scientific text, as well as to comprehending the ideas behind graphical representations of information. Information in science is often represented visually because it can be a highly impactful and efficient way to communicate. It can save time because the viewer can grasp concepts more quickly, and it can show trends and distribution, making prediction easier.
Graphic literacy becomes very important when information has been presented in a biased manner. Being able to spot this helps the viewer take bias into account when trying to see science objectively.
EXAMPLE
The graph below shows greenhouse gas emissions of a fictional company over time. Someone looking at this might interpret that the company's greenhouse gas emissions are decreasing over time. However, if you notice the time span sections at the bottom, they are not presenting regular intervals.
Let's break down the anatomy of what most graphs contain for a better understanding of what you might encounter. We've labeled the different parts on the bar graph below, from our earlier example:
Scale is the total range of values on the x or yaxis. Units are the form of measurement of the values on the x and/or yaxis. In this graph, the unit is in "tons" of greenhouse gas emissions, but it can be "number of people," "years," etc. Axis labels are descriptions of what the values on the axis represent — in this example, "Time" for the xaxis and "GHG Output" for the yaxis.
This graph doesn't have a footnote, but sometimes footnotes are placed at the bottom of a graph to provide additional explanation or interpretation of the graph. Finally, data is the information that the graph displays as a whole.
Let's discuss some different types of graphs that are used in environmental science, for there are many.
Type of Graph  Example 

Bar graphs Bar graphs are used for showing differences in quantifiable characteristics across groups. Its common characteristics are an x and yaxis, and data is depicted using a vertical or horizontal bar. 

Histograms Histograms are used to show the frequency of various characteristics across groups. Like bar graphs, they commonly have an x and yaxis, with data depicted using a vertical or horizontal bar. 

Line graphs Line graphs are used to show a trend in a characteristic relative to changes in time, space, concentration, or other variables. They commonly have an x and yaxis, with data depicted as a line connecting data points. 

Scatter plots Scatter plots are used to show the relationship between two different characteristics. They commonly have an x and yaxis, with data depicted using individual dots for each data point. 

Pie charts Pie charts are useful for showing relative proportions of multiple characteristics or groups within a larger group. They commonly have no axes, but are shown as a circle with labeled subdivisions. 

Pictographs Pictogrphas are like a bar graph or histogram, where they commonly use images for values, or they may use the relative size of an image to represent various values for comparison purposes. 

Flow diagrams Flow diagrams are used to show process, sequence, or flow, and may be multidirectional or weblike. They commonly have no axes, but they use arrows to show the direction of the process by connecting images, or they use text to represent each step. 

Maps Maps are used to depict differences in some characteristics, or to show the location of various phenomena. They commonly are a map of a region with icons, lines and arrows, and/or coloration, like the map shown below. 
Source: Adapted from Sophia instructor Jensen Morgan, BAR CHART CC HTTP://BIT.LY/1ZJR3OR HISTOGRAPH CC HTTP://BIT.LY/1CW91GA LINE CHART CC HTTP://BIT.LY/1WI3DYU SCATTER PLOT CC HTTP://BIT.LY/1WI3MLQ PICTOGRAM CC HTTP://BIT.LY/1AIKTDH KYOTO MAP PD HTTP://BIT.LY/1JZMMMI