Human Development In

dex

Groups

Human Development Index Groups average, 2013

The Human Deve

lopment Index (H

DI) is a measurement of a country’s acheivements in three areas: longevity, Very High

World

0.702

Medium human development

0.614

knowled

ge and sta

ndard of liv

ing. Longevity is m

easured by life expectancy at birth; knowlegde is measured High

Very high human development 0.890

Low human development

0.493

by a co

mbination of th

e adult li

teracy rate and the combined gross primary, secondary and tertiary school Medium

High human development

0.735

enrolm

ent ra

tio; st

andard of liv

ing is measured by GDP per Capita.

Low

Afghanistan

Albania

Algeria

Andorra

Angola

Antigua and Barbuda

Argentina

Armenia

Australia

Austria

Azerbaijan

The Bahamas

Bahrain

Bangladesh

Barbados

Belarus

Belgium

Belize

Benin

Bhutan

Bolivia

Bosnia and Herzegovina

Botswana

Brazil

Brunei

Bulgaria

Burkina Faso

Burundi

Cambodia

Cameroon

Canada

Cape Verde (Cabo Verde)

Central African Republic

Chad

Chile

China

Colombia

Comoros

Congo

Congo, Democratic Republic of the

Costa Rica

Côte d'Ivoire (Ivory Coast)

Croatia

Cuba

Cyprus

Czech Republic

DenmarkDjibouti

DominicaDom

inican Republic

EcuadorEgypt

El SalvadorEquatorial Guinea

EritreaEstonia

EthiopiaFiji

FinlandFrance

GabonThe Gam

biaGeorgia

Germany

GhanaGreece

Grenada

Guatem

alaG

uineaG

uinea-BissauG

uyanaH

aitiH

ondurasH

ungaryIceland

India

IndonesiaIran

Iraq

Ireland

Israel

Italy

Jamaica

Japan

Jordan

Kazakhstan

Kenya

Kiribati

South Korea

Kuwait

Kyrgyzstan

Laos

Latvia

Lebanon

Zimbabwe

Zambia

Yemen

Vietnam

Venezuela

Vanuatu

Uzbekistan

Uruguay

USAUnited KingdomUnited Arab Emirates

UkraineUganda

TurkmenistanTurkey

TunisiaTrinidad and TobagoTongaTogo

East Timor (Tim

or-Leste)

Mac

edon

ia (F

.Y.R

.O.M

.)

ThailandTanzania

TajikistanSyriaSwitzerland

SwedenSwazilandSurinameSudanSri L

ankaSpain

South Africa

Solomon IslandsSloveniaSlovak

iaSingaporeSierr

a LeoneSeyc

hellesSerb

iaSenegal

Saudi A

rabia

São Tomé and Prín

cipeSam

oa

St Vincen

t and th

e Gren

adinesSt

Lucia

St Kitts

and N

evisRwan

daRussia

Roman

iaQatar

Portu

galPolan

d

Philip

pinesPe

ru

Para

guay

Papu

a New

Gui

nea

Pana

maPa

lau

Pakis

tanOm

an

Nor

way

Nig

eriaNig

er

Nica

ragu

a

New

Zea

land

Net

herla

nds

Nep

al

Nam

ibia

Mya

nmar

(Bur

ma)

Moz

ambi

que

Mor

occo

Mon

tene

gro

Mon

golia

Mol

dova

Mic

rone

sia, F

eder

ated

Sta

tes o

f

Mex

ico

Mau

ritiu

s

Mau

ritan

ia

Mal

taMal

i

Mal

dive

s

Mal

aysi

a

Mal

awi

Mad

agas

car

Luxe

mbo

urg

Lith

uani

a

Liec

hten

stei

n

Liby

a

Libe

ria

Leso

tho

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.004

Population

7

Tropical environments Tropical environments158

Vegetation characteristics Tropical rainforest vegetation The tropical rainforest is the world’s most biodiverse ecosystem, however it is also incredibly fragile. This is because the species that live in rainforests have adapted to the constant high temperature and humidity and, due to the fact they are so specialised, their food sources are limited. This means that if deforestation occurs, it is very difficult for the rainforest to return to its original state. The Net Primary Productivity (NPP) is the amount of organic material produced by plants and available to herbivores. It varies dramatically between ecosystems and is determined by heat, water and nutrient availability, age and the health of the plant species. The NPP for the tropical rainforest is 2200 g/m²/year compared to the savanna, which has NPP of 990 g/m²/year. Due to the fact that there are no seasons in the tropical rainforest trees shed their leaves throughout the year. The trees are tall and thin with a crown of leaves at the top and buttress roots at the bottom. Buttress roots serve a dual purpose; they prevent the tree from falling over and they gather nutrients over a wider area.

Trees in the rainforest broadly grow in three layers. The emergent layer is composed of those trees that have grown rapidly to reach the sunlight, thus overshadowing their competitors. Trees are typically between 45 and 50 m in height although they can reach 70 – 80 m on occasion. Species that live in the emergent layer include the harpy eagle, the sparrowhawk, the vampire bat and the gibbon. The canopy is composed of trees that reach 25–30 m in height. This layer is dense and almost continuous and so blocks out 70–80 per cent of the available light. The fauna is similar to that which is found in the emergent layer although it is more diverse; the canopy is estimated to be home to a quarter of all insect species. Epiphytes (plants that grow harmlessly upon other plants) are abundant in this layer and include ferns, orchids and bromeliads. There are also lianas (long-stemmed, woody vines) that are rooted in the soil but use the canopy trees as a vertical support to climb to access the sunlight. The final layer of trees is the understorey, which receives only about 5 per cent of the available sunlight, although where the canopy is broken by falling trees the understorey vegetation is much denser. Plants in the understorey tend to have large, colourful flowers so that the animals and insects that carry their pollen can find them in the dim light. The high humidity in this layer suits amphibians such as salamanders and frogs; tree frogs have evolved feet with tiny suction pads

figure 7.18 Tropical rainforest, Amazonia, Brazil

figure 7.19 Daintree Rainforest, Queensland, Australia

figure 7.20 Cross section of rainforest layers

216342_A-level Geography_Ch07.indd 158 7/28/15 6:20 PM

Tropical environments Tropical environments 159

covered with sticky mucus that help them to hold onto branches. Below the tree layers the forest floor is covered with decaying vegetation, which decomposes rapidly due to the hot and humid climate.

Savanna vegetation Savanna vegetation includes a mosaic of grasses, trees and shrubs that have adapted to survive the dry season. Species are xerophytic (adapted to drought) with adaptations that include deep tap roots to reach the water table and sunken stomata on the leaves to reduce moisture loss. Species are also pyrophytic (adapted to fire) meaning that many trees have a thick bark, a large amount of biomass (stored energy) below the ground and the ability to regrow rapidly after burning. Savanna grasses have their growth tissue located at the base of the shoot close to the soil surface so that burning or grazing actually encourages its growth. Examples of plant species in the savanna include the acacia, palm and baobab trees and elephant grass, which can grow over 5 m tall.

Nutrient cycling: Gersmehl diagrams, soil fertility, energy flows and trophic levels Within ecosystems, nutrients are circulated and reused frequently. Macronutrients (those used in large quantities) such as oxygen, carbon, hydrogen and nitrogen and micronutrients (trace elements used in small quantities) such as magnesium, sulfur and phosphorus can all be absorbed by plants. Animals eat the plants and take on the nutrients. The nutrients are eventually returned back to the soil when the plants and animals die and are broken down by decomposers. All nutrient cycles involve stores and flows between the soil, litter and biomass, the proportions of which can be shown in the Gersmehl diagram (Figure 7.22). In the tropical rainforest the warm humid climate results in a high input of nutrients from weathering and precipitation. The continual growing season means that most of the nutrients are held in biomass storage; however, there are few nutrients held in the litter layer as the breakdown of nutrients is rapid. Where trees have been removed, precipitation is not intercepted and nutrients are leached out of the soil store; as a result, rainforest soils are relatively infertile despite appearances. In contrast, the biomass and litter stores in the savanna are relatively small as a result of the shorter growing season and fire respectively. The soils are quite fertile as most of the nutrients are found in this store so they are not burnt or leached out of the system.

The main driving force in terms of energy within an ecosystem is the Sun – it provides the energy required for photosynthesis and drives the hydrological cycle. The flow of energy can be shown in food chains and webs, which are the natural systems in which organisms feed on each other to survive. An organism’s place within that web is the trophic level. There are four trophic levels; primary producers, primary consumers, secondary consumers and tertiary consumers. Between each trophic level it is estimated that there is a 90 per cent loss of energy, which is a result of respiration and excreta. In the tropical rainforest the primary producer trophic level consists of ferns, bamboo and moss. Insects, spiders, fish and parrots are the herbivores that eat the producers; they are known as primary consumers. The secondary consumers, which eat the primary consumers, are animals such as bats, amphibians and reptiles whilst the tertiary consumers, which are at the top of the food chain, include snakes and carnivorous mammals such as jaguars. In contrast, savannas are dominated by tall grasses, which are the main primary producers, however shrubs and sparse trees such as the acacia are also found within this trophic level. Primary consumers include giraffes, antelopes, wildebeests, elephants, rhinos and, in Australia, kangaroos. These herbivores frequently

figure 7.21 Acacia savanna, Taita Hills, Kenya

Litter

Soil

UptakePathway

Precipitation

Circles -

Arrows -

compartments size proportional to amounts of nutrient storedwidth proportional to amounts of nutrient flow

RunoffDecay Pathway

Fallout Pathway

Weathering

Leaching

Biomass

figure 7.22 Gersmehl diagram to show nutrient cycling in the tropical rainforest

Litter

Soil

UptakePathway

Precipitation

Circles -

Arrows -

compartments size proportional to amounts of nutrient storedwidth proportional to amounts of nutrient flow

RunoffDecay Pathway

Fallout Pathway

Weathering

Leaching

Biomass

figure 7.23 Gersmehl diagram to show nutrient cycling in the tropical savanna

216342_A-level Geography_Ch07.indd 159 7/28/15 6:20 PM