what will happen if the world is without any other animals except humans

If the world were to have no other animals except humans, several significant consequences would arise:

1. Ecological Impact: Animals are integral parts of various ecosystems, and their absence would disrupt ecological balance, leading to unforeseen cascading effects on plant life and habitats.

2. Loss of Biodiversity: Biodiversity is essential for maintaining ecosystem services, which include regulation of ecosystems, such as pollination, seed dispersal, and pest control.

3. Pollination Issues: Many plants rely on insects and other animals for pollination. Without these pollinators, there would be a significant impact on agriculture and food production.

4. Disruption of Food Chains: The loss of animals would fundamentally alter food chains, with potential collapses of ecosystems that depend on predators, herbivores, and decomposers.

5. Decreased Soil Fertility: Many animals play roles in recycling nutrients and maintaining soil health, which is vital for plant growth.

6. Impact on Human Health: Some animals are essential for medical research and the development of new drugs, including those derived from substances found in animal venom or bodies.

7. Cultural and Psychological Effects: Animals have been a part of human culture and folklore throughout history. Their absence could lead to a sense of isolation and loss, affecting mental health and cultural richness.

8. Economic Implications: Industries that rely on animals, such as livestock farming, fisheries, and tourism, would collapse, leading to economic losses and unemployment.

9. Increased Disease Risk: Some animals can serve as reservoirs for diseases, and their absence might alter the dynamics of disease transmission among humans, potentially leading to unforeseen health crises.

10. Loss of Indicator Species: Animals often serve as indicators of environmental health. Without them, it would be harder to detect problems early.

Such a scenario would fundamentally change Earth's ecosystems and could have profound and largely negative impacts on the environment and human society.