Climate and natural vegetation Revision Notes

Climates vary significantly in temperature patterns, which can be analysed by examining the average temperatures of the hottest and coolest months and calculating the annual temperature range (difference between these two averages). For example, an equatorial climate typically has a small annual temperature range, often less than 5°C, with consistently high temperatures around 25–28°C throughout the year. In contrast, a hot desert climate experiences a much larger annual temperature range; daytime temperatures can exceed 40°C in the hottest months, while nights and cooler months may drop below 10°C, resulting in ranges often exceeding 20°C.

Understanding these temperature patterns helps explain the living conditions and adaptations of plants and animals in each climate. For instance, the stable warmth in equatorial regions supports dense, evergreen tropical rainforests, while the extreme heat and cooler nights in deserts limit vegetation to drought-resistant species.

• Annual temperature range = Average temperature of hottest month − Average temperature of coolest month
• Equatorial climates: small annual temperature range, consistently warm
• Hot desert climates: large annual temperature range, very hot days, cooler nights

Precipitation varies greatly between equatorial and hot desert climates, influencing ecosystem types. Equatorial climates receive high annual rainfall, often exceeding 2000 mm, mainly through convectional rainfall caused by intense solar heating that warms the ground, causing moist air to rise, cool, and condense into heavy afternoon showers. Relief rainfall also occurs where moist air is forced to rise over mountains, cooling and releasing precipitation.

In contrast, hot desert climates receive very low annual rainfall, often less than 250 mm, which is highly seasonal and unpredictable. Rainfall is usually brief and intense, sometimes caused by rare convectional storms. The scarcity and irregularity of rainfall limit soil moisture and vegetation growth.

These precipitation patterns are critical for understanding the distribution of natural vegetation and soil types in these climates.

• Equatorial rainfall: high, convectional and relief rainfall, evenly distributed
• Hot desert rainfall: low, seasonal, often brief and intense
• Precipitation influences soil moisture and vegetation density

Several key factors determine the temperature and precipitation patterns of climates:

Latitude: Equatorial regions near the equator receive direct sunlight year-round, resulting in high temperatures and convectional rainfall. Deserts often occur near 30° latitude where descending air in high-pressure systems inhibits rainfall.

Pressure systems: High-pressure zones suppress cloud formation and precipitation, common in deserts; low-pressure zones encourage rising air and rainfall, typical of equatorial regions. Winds associated with these systems influence moisture transport and temperature moderation or extremes.

• Latitude affects solar angle and temperature
• Pressure systems influence air movement and rainfall
• Winds transport moisture and affect temperature
• Proximity to oceans moderates temperature and provides moisture
• Altitude causes temperature decrease with height, affecting local climate
• Ocean currents can warm or cool coastal areas, influencing climate

Climate directly shapes natural vegetation, which in turn influences soil development and wildlife habitats. In tropical rainforests, warm temperatures and abundant rainfall support dense, multilayered vegetation with rapid nutrient cycling. Soils tend to be nutrient-poor due to heavy leaching but are rich in organic matter from decomposing plant material. Wildlife is diverse and adapted to the complex forest structure.

In hot deserts, extreme temperatures and minimal rainfall limit vegetation to sparse, drought-resistant plants like cacti and shrubs. Soils are often sandy or rocky with low organic content. Wildlife includes species adapted to conserve water and tolerate heat, such as reptiles and nocturnal mammals.

These ecosystems demonstrate how climate controls the physical environment and biological communities in a tightly linked system.

• Tropical rainforests: warm, wet climate supports dense vegetation and diverse wildlife
• Soils are nutrient-poor but rich in organic matter
• Hot deserts: hot, dry climate limits vegetation and wildlife diversity
• Soils are dry, sandy, and low in organic matter

Deforestation involves the removal of forest cover, often for agriculture, logging, or urban development. Causes include expanding farmland, commercial logging, mining, and infrastructure projects.

Consequences are severe both locally and globally: locally, loss of habitat threatens biodiversity, disrupts soil stability leading to erosion, and alters water cycles causing reduced rainfall and increased flooding. Globally, deforestation contributes to increased atmospheric carbon dioxide, exacerbating climate change. It also affects indigenous communities dependent on forests for livelihoods.

Efforts to manage deforestation include sustainable forestry, protected areas, and reforestation projects, which aim to balance human needs with environmental conservation.

• Causes: agriculture, logging, mining, urbanisation
• Local impacts: habitat loss, soil erosion, altered water cycles
• Global impacts: increased CO2, climate change
• Human impacts: loss of resources and livelihoods