Habitat loss and fragmentation, over-exploitation, alien species invasion, and co-extinction are causes for:

Concept: 

• The diversity of creatures in an ecosystem is referred to as biodiversity.
• However, an ecosystem's biodiversity is lost when the available resources are overused, the habitat is fragmented, or an alien species invades the area.

Explanation:

Option 1: 

• Natality refers to the number of births during a given period in the population that are added to the initial density. 
• Therefore, this is the incorrect option.

Option 2: 

• When the population surpasses its carrying capacity, there is a dramatic surge in population.
• This is called population explosion. Therefore, this is the incorrect option.

Option 3:  

• Competition can be defined as a process whereby one species' fitness is significantly lower in the presence of another species. 
• Therefore, this is the incorrect option.

Option 4: 

• Habitat loss and fragmentation, over-exploitation, alien species invasion, and co-extinction are causes of biodiversity loss.
• Habitat loss and fragmentation lead to the extinction of plants and animals.
• Over-exploitation leads to the loss of flora and fauna. Example: Many marine fish populations around the world are overharvested, endangering the continued existence of some commercially important species.
• Alien species invasions: When alien species are introduced unintentionally or deliberately for whatever purpose, some of them turn invasive, and cause the decline or extinction of indigenous species.
• For example, the Nile perch introduced into Lake Victoria in east Africa led eventually to the extinction of an ecologically unique assemblage of more than 200 species of cichlid fish in the lake.
• Co-extinctions: When a species becomes extinct, the plant and animal species associated with it in an obligatory way also become extinct.
• For example, When a host fish species becomes extinct, its unique assemblage of parasites also meets the same fate.

So, the correct answer is option 4.