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Certain concepts or relationships are much clearer when an explanatory figure is provided:

However, to an extent, increased rainfall also allows for vegetation growth, which, as seen, decreases the amount of surface run off. This creates a curve for sediment yield relating to rainfall, creating a peak in sediment yield at a particular level of precipitation, as will be discussed.

The reference to a curve relating sediment yield absolutely cries out for a diagram (but sadly none was provided). Why discuss something when you can convey the same information more effectively (and in a fraction of the time) with a diagram?

Compare this description (which didn’t include a diagram):

It is this general trend in concurrence with extinction rates that forms the equilibrium theory. MacArthur and Wilson (1967) explain that, when an island first forms and has not yet been colonised by any species, it has the greatest potential for colonisation but its extinction rate is zero due to the absence of species. As species start to colonise the island, the immigration rate is at its peak and the extinction rate gradually begins to increase. The immigration rate starts to decelerate as more species colonise the island because the potential for colonisation is reduced, whilst extinction rates accelerate due to greater competitive exclusion of species. Though there is variability in immigration and extinction rates within and between islands, the model graph would show two concave curves running in opposite directions; their point of intersection marking the equilibrium number of species that island is capable of supporting.

With this one on the same topic (written by a supervisor):

Simply put, the theory of island biogeography proposes to explain species richness through immigration and extinction rates . Immigration is said to be affected by distance of the island from a source of colonists, usually the mainland. This is known as the distance effect, with increased isolation leading to decreased immigration. On the other hand, extinction is put as a function of island area, with large islands having lower rates of extinction. On the basis of these area and distance controls, immigration and extinction rates, for a particular island, tend to an equilibrium limit of species richness. This thesis is illustrated in MacArthur and Wilson’s (1967) diagrams (see Figure 1 and Figure 2).


        Figure 1                                                                     Figure 2

Note how the author refers to the figures in the text.