What usually happenstance an ecosystem after a sudden catastrophic change?

Please help

Succession occurs after sudden catastrophic change.

Explanation:

In communities, organisms occupy specific niches. These gradually evolve over time as these organisms interact with their geosphere. In ecological succession, a community may undergo several dynamic changes. These include primary succession and secondary succession- these communities eventually try to achieve equilibrium over time.

After catastrophic events, the microorganisms, primary succession occurs. Here, a colonizing species exploits a non-habitable region. These eventually make the region more habitable through nutrient cycling, weathering, etc. which ushers in secondary succession. Here, the communities become more complex with time, becoming more varied and an increasingly large food web.

they had the law tat factories that produces smoke cannot be built near residential buildings.

building of proper sewage system was done to ensure that the waste is carried away from the humans so that they do not get diseases from it.

also they built water systems to provide water in those areas which are drought prone.