Facts:

• Located in Southern USA and Northern Mexico
• Summer temperatures can reach 48°C
• Diurnal range of 15°C

Vegetation:

• Saguaro cactus
  → Up to 15m tall
  → Lives for up to 175 years
  → Stem can expand as it fills with water
  → Ribbed stem reduces wind speed, water loss
  → Sunken stomata reduces water loss
  → Shallow roots to quickly absorb water from storms
• Palo Verde
  → A drought-tolerant tree
  → During the dry season, it sheds its leaves
  → Green bark allows photosynthesis
• Creosote bushes
  → Small dark leaves reduce transpiration (water loss)

Animals: >500 species of animals

• Kangaroo rat
  → Does not need to drink water, it gets water from food
  → Hides in burrows during the day to avoid the heat
  → Highly concentrated urine, dry droppings reduce water excreted
  → No perspiration
• Gila woodpecker
  → Burrows into saguaro cacti for home
• Jackrabbit
  → Large ears with blood vessels to lose body heat quickly
• Most animals are nocturnal

Human impact:

• Rapid expansion of cities increased groundwater extraction, lowered the water tables
• Roads and barriers prevent animal movement
• Overgrazing of cattle reduces food for native animals
• Exotic species displace native species

Last updated: Apr 2025