1. Mammals
1.1. Warm- blooded
1.1.1. Give birth
2. Lack of food/water
2.1. malnutrition
2.2. famine
2.2.1. starving
2.2.1.1. ravening
2.3. hunger
2.4. nutritional deficiency
2.5. poor diet
2.6. go hungry
2.7. run out of water
2.8. water scarcity
2.9. Death
3. Overpopulation
3.1. Overcrowding
3.1.1. Fertility treatment
3.2. Poverty
3.3. congestion
3.4. Birth
3.4.1. Death
3.5. Inmigration
3.6. Developing countries
3.7. inhabited
3.8. Child labor
3.8.1. Lose education
3.9. Live longer
3.10. Lack of water
3.11. excess
3.12. bottleneck
3.13. mass
3.14. rubber-necking
3.15. traffic-jam
4. Global warming
4.1. Natural
4.2. Climate change
4.2.1. Human activity
4.3. Rise of sea levels
4.4. Severe precipitation
4.5. Man-made
4.6. Rainfall
4.7. Fossil fuel
4.8. Carbon dioxide
4.9. Greenhouse effect
4.10. Glaciers melting
4.11. Atmosphere
4.11.1. Heat
4.11.1.1. Sun
4.12. Wildlife
5. Environment
5.1. habitat
5.1.1. ecological
5.2. environment friendly
5.3. flora and fauna
5.4. climate
5.4.1. environment protection
5.5. nature
5.5.1. nature conservation
5.6. semi-arid conditions
5.7. Deforestation
5.8. Desiccate
5.9. ecosystem
5.10. ozone layer
5.10.1. reciclyng
5.11. wind-power
5.12. organic
5.13. chemicals
6. Humans
6.1. Homo
6.1.1. humans beings
6.1.1.1. Reproductive
6.2. Person
6.2.1. human race
6.3. Man
6.3.1. anthropological
6.3.1.1. ethological
6.4. Woman
6.5. Intelligence
6.5.1. soul
6.6. Speech
6.6.1. Respiratory
6.7. Earth
6.8. Feelings
6.8.1. Heart
6.8.1.1. Lungs
6.9. Mind
6.9.1. Brain
6.10. Consciousness
6.11. Body
6.11.1. Organs
6.11.1.1. Blood
7. Noise
8. Wildfires
8.1. Fuel
8.2. Air
8.3. Heat Sources
9. Thunderstorm
10. Animals
10.1. Amphibians
10.1.1. Cold-blooded
10.1.1.1. Lay eggs
10.2. Reptiles
10.2.1. Scales
10.2.1.1. Dry skin
10.3. Fish
10.3.1. Cold- blooded
10.3.1.1. Scales
10.3.1.1.1. Fins
10.4. Birds
10.4.1. Lay eggs
10.4.1.1. Warm blooded
10.4.1.1.1. Feathers
10.5. Wild
10.5.1. Soil
10.5.1.1. Fertilizers
10.5.1.1.1. Pesticides
10.6. Endangered
10.7. zoological
11. Pollution
11.1. Air
11.1.1. Smokes
11.1.1.1. Factories
11.1.1.1.1. Car
11.2. Water
11.2.1. Litter
11.3. Harmful
11.4. The 3 R`s
11.4.1. reduce
11.4.1.1. reuse
11.4.1.1.1. recycle
11.5. Radiation
12. Natural Disasters
12.1. Tornadoes
12.1.1. Thunderstorms
12.1.2. Wind in Rotation
12.1.3. Supercells
12.2. Tsunamis
12.2.1. Underwater
12.3. Volcanoes
12.3.1. Lava Rivers
12.3.2. Geological Architects
12.3.3. Liberates Nutrients
12.3.4. Creates Fertile Soils
12.4. Hurricanes, cyclons and typhones
12.5. Earthquakes
12.5.1. Fault Zone
12.5.2. Tectonic Plates Collide
12.5.2.1. Collide each other
12.5.2.2. Stretched or Squezzed
12.5.3. Saesmic Waves
12.6. Floods
12.6.1. Exesiive rain
12.6.2. Ruptured levee or dam
12.6.3. Melting of Snow or Ice
12.6.4. Rising Seas
12.6.5. Climate Changes
12.7. Landslides/Landslip
12.8. Avalanches
12.8.1. Starting Zone
12.8.2. Track
12.8.3. Runout Zone