The succession in reverse direction due to adverse conditions is termed as ...........

Explanation

**Step-by-Step Solution:**

1. **Understanding Succession**: Succession refers to the process of change in the species structure of an ecological community over time. It can occur in a variety of environments and can be influenced by various factors.

2. **Types of Succession**: There are two main types of succession:
- **Progressive Succession**: This is the forward direction of succession where the ecosystem becomes more complex and diverse over time. It typically involves the establishment of new species and improvement of environmental conditions.
- **Retrogressive Succession**: This is the reverse direction of succession, where the ecosystem deteriorates due to adverse conditions. It involves a decline in species diversity and complexity.

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