Corrected version:

The provided pie chart and tabular chart demonstrate the major causes of why agricultural land became less productive and affected regions around the world during the 1990s.

Explanation: 

• "demonstrates" should be changed to "demonstrate" to match the subject "pie chart and tabular chart."

• "agriculture land" should be corrected to "agricultural land."

• "affected their regions" should be changed to "affected regions" for clarity.

• "of the world" has been added for clarity.

• "the period of 1990s" has been changed to "during the 1990s" for better phrasing.

Improved version:

The provided graphical representations, including a pie chart and tabular data, offer valuable insights into the prominent factors leading to decreased agricultural productivity and their global impact during the 1990s. 

Corrected version:

In an overview, at first glance, it can be clearly inferred that the highest percentage of overgrazing occurs in Oceania. 

Explanation: 

• "it can be clearly inferred that high" should be corrected to "it can be clearly inferred that the highest."

• "cost" should be changed to "occurs" to better convey the idea.

• "in" has been added for proper phrasing.

Improved version:

Upon initial scrutiny, it becomes distinctly apparent that the region of Oceania faced the most substantial land degradation, primarily as a result of overgrazing.

Corrected version:

Regarding information about the causes of worldwide land degradation in the 1990s, the highest share was due to overgrazing, accounting for 30% of the total. 

Explanation: 

"Regarding information for causes" has been changed to "Regarding information about the causes" for clarity.

"shares by the overgrazing" has been corrected to "share was due to overgrazing" to convey the information more clearly.

"and 30% of deforestation" has been rephrased to "accounting for 30% of the total" for better structure and clarity.

Improved version:

Concerning the underlying causes of worldwide land degradation in the 1990s, overgrazing emerged as the predominant factor, accounting for a significant 30% of the total degradation. 

Corrected version:

Moving further, more than a quarter was attributed to over-cultivating, while only 7% of land degradation was caused by other activities.

Explanation:

• "was by over cultivating" has been changed to "was attributed to over-cultivating" for clarity.

• "land gradation" has been corrected to "land degradation" to use the appropriate term.

• "by other activities" has been added for clarity and proper structure.

Improved version:

Delving deeper into the data, it is revealed that over-cultivation contributed to slightly more than a quarter of land degradation, while other activities accounted for only 7% of the overall degradation. 

Corrected version:

Turning to the data for causes of land degradation by region, firstly, in North America, only 0.2% of the land degraded due to deforestation, and 1.5% resulted from overgrazing, making the total land degradation 5%. 

Explanation: 

• "Turning to the data for causes" has been corrected to "Turning to the data for the causes" for proper phrasing.

• "north America" has been changed to "North America" to capitalize the region name.

• "only 0.2% of land degraded by deforestation" has been rephrased to "only 0.2% of the land degraded due to deforestation" for clarity.

• "and 1.5 by over-grazing" has been changed to "and 1.5% resulted from overgrazing" for clarity and consistency.

• "which total land degraded was 5% only" has been restructured for better clarity.

Improved version:

Turning our attention to the regional breakdown of land degradation causes, North America experienced minimal land degradation, with only 0.2% attributed to deforestation and 1.5% to overgrazing, resulting in an overall land degradation rate of 5%. 

Corrected version:

In Europe, there was the highest percentage of land degradation at 23%, while Oceania had a 30% proportion of total land degradation.

Explanation:

• "In Europe, had the highest percentage of land" has been changed to "In Europe, there was the highest percentage of land degradation at 23%" for better structure and clarity.

• "Oceania had 30% proportion of total land degradation" has been rephrased for better clarity.

Improved version:

In contrast, Europe witnessed the highest proportion of land degradation at 23%, while Oceania represented a staggering 30% of the total land degradation.