Shrublands – Biomes Episode 3

Shrublands – Biomes Episode 3


Often overlooked, these relatively arid regions
of earth take second or third place to forests or grasslands when it comes to beauty contests. Too dry for trees to flourish, we’re left
with a mix of shrubs and grasses, spanning the subtropics to the temperate latitudes. Having a surprising biodiversity considering
their parched appearance, these areas are known by an equally diverse set of names,
from scrub or scrubland, to bush, brush matorral and chaparral. A place of heat and drought, yet still abundant
life, these are the shrublands of our planet. Shrublands are a relatively open form of country
that regularly experiences drought. The defining vegetation is shrubs and grasses. Shrubs, like trees, are woody plants that
possess lignin that allows the plant to retain the growth of previous years and build upon
it with new growth the following year, as opposed to grasses and other plants that die
back and must start again from rootstock or even new seed in the next growing season. In contrast to trees, however, shrubs are
stunted in growth, and typically do not exceed 5 metres in height from a single stem, or
10 metres if multi-stemmed. But where shrubs lack height, they make up
for in hardiness, and in comparison to trees are much more drought-tolerant, allowing them
to thrive in many regions of the world where trees are absent. These areas are always the result of a severe
dry season, or irregular patterns of rain that lead to very long droughts, but occur
in two very different climate types. In the case of the subtropics, shrublands
are simply transitions between the savannah and desert, where alternate wet and dry seasons
exist, but where the wet season is of insufficient weight or length to allow tree growth. Such Koppen climate zones in this case would
be in the crossover of Tropical Savannah (Aw), and Hot Semi Arid (BSh) areas. But shrublands are best known for being found
in the temperate latitudes of the Mediterranean basin and in other parts of the world that
have the Mediterranean climate of a hot, dry summer and a cool wet winter (Csa). Despite being temperate, this unique climate,
the only one with a dry summer and wet winter, creates a particular stress on plants, where
the dry season occurs at the hottest time of the year – evapotranspiration from the
plants is greatest when the least amount of water is present in the soil. No trees are able to survive these conditions,
despite the winter rain, and so instead, we find a mix of shrubs and grasses. If we consult our Holdridge Lifezones chart,
we can find these areas as desert scrub, spanning the tropics through to more temperate regions,
but always where the annual rainfall is relatively low. Shrubs can also exist as the principal vegetation
in the transition between boreal forest and tundra in the far polar latitudes. But as these conditions are so different to
the other two mentioned, and are principally a result of insufficient summer temperatures,
we’ll discuss these areas in the relevant future episode. With such severe dry seasons, it’s no surprise
that fires are common in these regions, and at some point all of us will have seen on
the news brushfires threatening the fringes of Los Angeles or in parts of the Mediterranean. Growing up in Adelaide, Australia, which is
within this biome, I personally recall seeing a blackened sky on the horizon as fires would
engulf the surrounding brush after a long dry summer. So where in the world do we find the shrublands? Well, as mentioned, they occur in the subtropical
transition zones between savannah and desert, and also in the Mediterranean climate zones
of the temperate latitudes. We’ll first take a look at the subtropical
scrub areas, starting with the band that surrounds the Sierra Madre mountains of Mexico, from
Texas down to central Mexico on the eastern side, and from Chihauhua down to Jalisco in
the west. On the NE tip of Brazil we find an extensive
thorn scrub known as Caatinga or “White Forest”, which is brought about due to fast
draining soils and irregular rainfall patterns and droughts, and is the driest part of this
large country. In the heart of South America, running down
the eastern side of the Andes in a wide plain from Bolivia, through Paraguay to Argentina,
we have the extensive scrubland known as El Gran Chaco, probably the largest such contiguous
area on Earth. Onto Africa and subtropical scrub acts as
a transition between the Savannah to the South and the Sahara desert to the north in a narrow
band that runs almost exactly east-west. Southern Ethiopia, Somalia and northern Kenya
also have extensive scrub areas, as do parts of Botswana and Namibia, again acting as transitions
between Savannah and desert. In India – we have two distinct bands of
scrub, one in West India which is a transition between the Thar desert of the west, and the
more fertile plains of the centre. The other runs down the central and eastern
part of the Deccan plateau, and is formed due to rain shadow from the prevailing SW
Monsoon. The last area that features subtropical scrub
occurs in northern Australia, again acting as a transition zone between the northern
savannah and semi-arid heart of the island continent. In the five Mediterranean climate zones of
our planet we have the other, temperate, form of shrublands, resulting from hot and dry
summers. In Southern California, this is known as Chaparral,
and still extensively covers the hills from Santa Barbara, through Los Angeles, and San
Diego and down past Tijuana into the northern Baja peninsula. In Central Chile we have a narrow strip of
scrub between the Pacific Ocean and the Andes mountains known as Mattoral, named by settlers
after the equivalent biome found in Spain. In the Mediterranean basin itself, we have
the largest area of temperate scrub, running from southern Portugal in the West, into the
Mattoral that covers large parts of Spain, while in north Africa, the northern parts
of Morocco, Algeria and Tunisia are dominated by this biome. In Southern France, the scrub is known as
Maquis and Garrigue, depending on elevation and vegetation density. Sardinia, Sicily and the west coast of Italy
also have this biome, where it is known as La Macchia Greece is dominated by scrub, where it is
known as Phrygana (Φρύγανα), and this Mediterranean scrub extends into significant
parts of Turkey, as well as Cyprus and finally Lebanon and Israel at the sea’s eastern
end. Most of the southern cape of Africa has narrow
band of temperate scrub where it is known as Karoo or Fynbos, which is the most biodiverse
of all scrubland areas, and possessing thousands of unique species found nowhere else. Lastly the south-western and south-central
parts of Australia have their own form of temperate scrub in large areas known as Mallee
and Kwongan, where dwarf forms of eucalyptus dominate. Plant species diversity in the shrublands
is high. If we look first at the subtropical scrub
areas, starting in Texas and Mexico, to the east of the Sierra Madre common species such
as Mesquite, Yucca and Prickly Pear cacti can be found. In the Caatinga “White Forest” of NE Brazil,
drought-hardened species such as Joazeiro, Bombacae and various cacti species such as
Facheiro are common. In the vast Chaco of Bolivia, Paraguay and
Northern Argentina, we find parklike vegetation of palms mixed with grasses in the wetter
parts, while in the drier areas, drought hardened shrubs like senna, as well as a number of
cacti species can be found. In the Sahel of Africa, the long band of scrub
to the south of the Sahara, we find dwarf acacias being the dominant species, while
other shrubs include myrrh, and spiny grasses such as Panicum. East of the Deccan plateau in India, thorny
scrub dominates, with Acacias, being the most common family also. Palms can be found in the wetter parts, while
the driest areas include hardy species such as Euphorbia. In northern Australia, the band of scrub separating
the Savannah and desert interior is dominated again by Acacias, especially the species Mulga
while spinifex and triodia grasses cover the ground. In terms of species and biodiversity, the
temperate shrublands are greater than the subtropical forms, and remarkably so when
considering the challenging drought conditions experienced each summer. Because the temperate scrub areas are isolated
from each other, each of these five zones has developed unique species that do not exist
in the other zones, although there are some common relations between the areas within
each hemisphere – for instance California and Mediterranean areas both have oaks, while
Acacias can be found in Chile, South Africa and Australia. Looking in detail at each of these five areas,
and in California we can find a variety of oaks that are stunted due to the summer drought
conditions, such as the Coast Live Oak, as well as a variety of Manzanitas or Bearberrys,
Garrya, Rhus and Ceanothus. In Chile we find Acacia, Baccharis and Prosopis,
the latter occurring also on the other side of the Andes in the Chaco. As mentioned previously, the Fynbos biome
of the South African Cape has the largest number of scrubland species anywhere, with
prominent families including Aspalathus (from which Rooibos tea is made), Senecio and Erica
heathers. South-west and south-central Australia are
dominated by the mallee – dwarf eucalyptus which invariably grow as multi-stemmed plants
from underground tubers. Other prominent species include Banksia and
Conospermum. Lastly, in Europe and the Mediterranean basin
itself, we find a variety of dwarf oaks such as the Cork and Kermes Oaks, the Arbutus family
that includes the strawberry tree (no they aren’t actual strawberries), Cytisus and Pistacia. And finally, found throughout the Mediterranean
is the most famous of all scrubland plants – the olive tree (Olea Europaea). These “trees” are technically shrubs,
since they rarely grow beyond 10 metres in height, and are famed for their fruit which
produces oil consumed by humans for millennia. The plants are highly drought resistant, and
can live for thousands of years – that you could see some of the trees that Caesar or
Aristotle may have taken shade under is something to wonder at. Since shrubs have adapted to become highly
drought and fire tolerant, their foliage is not very nutritious and often contains toxic
chemicals, so animal numbers in these parts are typically low compared to Savannah or
forest. So while we might not hold the shrublands
as dearly as their big brother forests, these biomes nonetheless get plenty of airtime. If you’ve ever watched any American television
or movies, chances are you’ll have seen scrubland in outdoor shots, as so many movies
of the past were filmed out of Hollywood, and the countryside surrounding Los Angeles
is the type of Mediterranean scrub referred to as chaparral. This, incidentally gives us the word for “chaps”,
because the chaparral, like most shrublands can often be a giant thicket of thorny shrubs,
and leather protection to the legs was necessary to prevent being scraped to death while on
foot or horseback. And the shrubs of these regions, due to their
manageable size compared to trees, and their hardiness, have become favourites of the average
domestic garden not just in regions native to this biome, but in cooler and wetter climates
such as those of the United Kingdom, a long way from the parched and baked lands of the
scrub. And that is the shrublands. I hope you enjoyed my presentation of this
somewhat underrated biome. If you did, please like and share this video,
and let me know your thoughts in the comments. Don’t forget to subscribe, so you don’t
miss future episodes. Thanks again for watching, and for the next
episode, bring plenty of water, as we’ll be venturing into driest of all the biomes
– the deserts.

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11 thoughts on “Shrublands – Biomes Episode 3

  1. Honestly I get so happy when I see a new video from you, please don't stop making them. You seriously deserve more subs

  2. Geo, is there something that can extend the summers into the shoulder seasons without making mid-summer too hot, while simultaneously making the winter cold, probably making the winter same as in Moscow?

  3. A well presented introduction to this fascinating biome. I’m a resident of San Diego County, California, which has tremendous biodiversity amidst a variety of different shrubland types. During a wet winter some areas can appear almost lush. By the end of the annual summer drought the landscape takes on a somewhat barren and harsh look. Unfortunately little remains of undisturbed coastal chaparral.

  4. Do you think the climate of Cairo is Mediterranean? Considering the climate of Redding California is considered Mediterranean while summers are still hotter than Cairo.

  5. Actually there is a lot of forests in Mediterranean climate cause as you know . Mediterranean regions are mountaines . Some endemic trees like Cedar and Pine forests exist

  6. I've enjoyed this episode a lot! Thanks for preparing such beautiful and consistent work Ben! It is a very complex biome, having many factors of influence, including fire. I was really surprised about the extent biodiversity of South African Shrublands, with lots of endemic floristic species in such little and isolated area.

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