Download Chapter 4. Causes for Biodiversity Loss

Dutch Caribbean
Biodiversity Strategy
(draft version 10.2)
23rd December 2013
Chapter 4
Causes for Biodiversity Loss
Committee members:
Adrian Delnevo
Frank van Slobbe
Hannah Madden
DCNA Secretariat
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4. Causes of Biodiversity Loss
Main Threats
In order to preserve biological resources it is necessary to have a clear
understanding of the major threats within terrestrial, freshwater and marine
systems. Traditionally the identification of threats, such as insufficiently protected
areas, illegal trade and poaching, and introduced species has resulted in such actions
as greater protection, law enforcement, and non-native eradication programs. All of
these responses may be necessary, but they often respond only to part of the
problem. More fundamental problems may lie outside protected areas such as
pollution, settlement patterns, capital flows and other factors relating to a larger
international community.
Major threats to biodiversity include:

Increased human population and tourism visitation have resulted in
increased development, pollution, habitat loss, habitat degradation or
fragmentation, and wildlife disturbance

Over-harvesting, particularly overfishing, is a chronic threat to ecosystem
stability, with species being harvested at a higher rates than they can sustain
by natural reproduction

Pollution is a complex and all-pervasive issue and includes solid waste
management, atmospheric pollution, pollution by agricultural chemicals and
pesticides, nutrient and waste water, nitrate and phosphate run-off, salt
toxicity, and the release of many compounds of heavy metals from industrial
sources such as oil refineries. This has a negative impact not only on
terrestrial but also on adjacent marine ecosystems.

Climate change is causing a rise in atmospheric and oceanic temperatures
resulting in changed weather patterns, bleaching events, sea level rise and
ocean acidification. Other predicted impacts include increased storm activity
and intensity. The full impacts of global climate change are yet to be
determined and the drivers originate far from the areas most strongly
affected, such as the small islands of the Dutch Caribbean.

Introduced and invasive species, have had a dramatic effect on native flora
and fauna around the world, in some instances replacing or out-competing
native species. Introduced plants are a serious threat on all the islands and
probably represent the pre-eminent threat to terrestrial ecosystems.
Introduced and invasive fauna also pose a real and sustained threat to
ecosystems such as lionfish in the marine environment, and snakes, rats, cats
on land. Moreover, introduced herbivores (e.g., goats, donkeys) threaten
native flora and exacerbate habitat degradation.
The rapid destruction of the world’s most diverse ecosystems, especially in the
tropics, has led many experts to believe that the earth’s total biological diversity is at
serious risk of extinction in the next 20-30 years. The definition of rarity is now
understood to be more complex than previously envisaged. Understanding the
geographic range, habitat specificity and local population size underlies practical
conservation biology. Information on threats or ecological stressors will help
determine management strategy and subsequent prioritization.
Caribbean coral reefs have suffered massive loss of cover. The latest scientific review
(Status and Trends of Caribbean Coral Reefs 2013) states ”Coral cover has declined
by more than 80% since the 1970s, virtually all the large fishes, sharks and turtles are
gone”. The consequences include widespread collapse of coral ecosystems, increase
in large seaweeds (macro algae), outbreaks of coral bleaching and disease and
failure of corals to recover from natural disturbances such as storms and hurricanes.
Major region wide ecological events, which have recently had a negative impact on
coral reefs in the Dutch Caribbean include:
 Mass mortality of sea urchins (Diadema sp) in 1983
 White band disease outbreaks 1970s onwards which resulted in massive loss
of near shore coral reefs (Acropora sp)
 Repeated bleaching events and disease outbreaks from1990s onwards
 Lionfish invasion which effected the Dutch Caribbean from 2010 onwards
The signature for overfishing of coral reefs throughout the Caribbean is a long
standing feature of the scientific literature whilst the signature for global climate
change has only recently become apparent.
Protected Area Threats
The DCNA Management Success threat classification scheme has been developed
using IUCN Red List descriptors, WWF scoring with the inclusion of some detail that
has been gathered from conservation practitioners since the start of the
Management Success Project in 2004.
Six of the most significant threats facing the marine parks of the Dutch Caribbean
Threat
Detail
Invasive; Marine
predatory fauna
species
Lionfish are not native to the Caribbean and seem to have no
natural predators in the Caribbean. They are prolific feeders
and effective predators. They also reproduce and grow quickly
and are resistant to many parasites. The effect their rapidly
Waste Water;
Sewage
Overfishing & harvesting aquatic
resources;
Intentional (small
scale)
increasing population will have on the reefs is not yet fully
understood.
Nutrients are chemicals that are used by plants and animals
for growth and energy. The main nutrients used on coral reefs
are nitrogen and phosphorus compounds. Sewage from the
human population is the main source of nutrient pollution on
coral reefs. Corals usually thrive in nutrient poor
environments and coral reef ecosystems are designed to
quickly recycle any excess nutrients in the system. Any
damage to the corals on a reef will affect the whole reef and
the human use of the reef e.g. a decline in diving tourism
because damaged reefs are less attractive to visitors.
Artisanal and recreational fishing is a severe problem where
fish and crustacean stocks are directly under threat from local
fisherfolk targeting species for consumption and some smaller
commercial markets.
During heavy rainfall, water runs off the land directly into the
marine park. This is especially the case after sustained heavy
rain when the ground is soaked and during rain after a dry
period when the ground is hard and does not soak up rainfall
easily. Terrestrial runoff contains nutrients, sediment litter
and pollutants all of which affect the values of the marine
environment. Sediment or suspended matter is insoluble
particles of soil and other solid inorganic and organic
materials that become suspended in water Sedimentation is a
Waste Water; Run-off
natural process resulting from erosion of land and transport
of soil to the sea (terrigenous sediments), or from
resuspension of sediment previously deposited (such as
carbonate from coral reefs). The main sources of sediment
inputs to the marine environment are considered to be runoff
and sewage. Agricultural activities, deforestation,
urbanisation and poor land management are key human
activities that can increase run-off and consequently
sedimentation on coral reefs.
Building developments for tourism are often carried out near
to the water’s edge. This presents particular problems for
Residential &
pollutants entering marine parks through bad practice. When
commercial
it is windy or it rains, cement, bags and other site rubbish can
development
be blown or washed into the sea if preventative steps are not
taken. These can then cause considerable damage to coral
reef organisms, seagrasses and mangroves.
Climate change is often cited as a cause of spiking sea
Habitat shifting & temperatures, and a possible cause of increasing annual sea
alteration
temperatures. Warmer waters absorb more carbon, making
them more acidic. Increased temperatures and ocean
acidification cause coral bleaching and the attrition of other
species with calcareous skeletons. This is changing the
structure of coral reefs, reducing coral cover, increasing algae
cover and altering reef habitats. Many small open water
organisms that form an essential base for the food web; have
calcareous skeletons that will also be dissolved in warmer,
more acidic seas.
Six of the most significant threats facing the marine parks of the Dutch Caribbean
Threat
Small-holder
grazing, ranching
or farming
Invasive;
Terrestrial
predatory fauna
species
Invasive;
Terrestrial fauna
Invasive;
Terrestrial flora
Extreme rain
Detail
Domestic livestock that is allowed to roam and forage in wild
habitats, being supported by the resources offered by the parks
of the Dutch Caribbean. Goats, sheep, pigs, chickens, donkeys
and cows are farmed but not contained. Free roaming animals
cause significant damage to park environments cause extensive
damage to vegetation on large areas of land. The shrub layer
can be reduced to bare soil because of feeding preferences;
young shoots are eaten before having a chance to develop and
reproduce. Considerable erosion problems develop in heavily
grazed areas because there are no roots in the ground to help
bind the soil together.
Cats, dogs, rats, Boa (Aruba) and mongoose (St. Maarten) effect
bird, reptile and other small animal populations by eating adults
juveniles and eggs of native and vulnerable species.
Domestic livestock that has gone feral (goats, sheep, pigs,
chickens, donkeys and cows). There is no record of the numbers
of animals and there are no responsible owners. These animals
cause significant damage to park environments (see 2.3.2,
small-holder grazing).
Corallita (also known as Mexican Creeper) is a vine that is often
introduced as an ornamental species. It becomes a serious
threat to native plants and animals by forming dense
impenetrable thickets, smothering the natural vegetation,
killing the native species which changes the structure and
functions of habitats
One of the main environmental consequences of development
is erosion. Soil loss due to increased erosion does considerable
damage to terrestrial and marine resources, as the eroded
material is no longer available for plants to use on land and also
reduces water quality and smothers coral reef organisms. The
increased water running off the island also contains pollutants
such as oil from roads, and fertilisers that directly kill marine
organisms. The rainwater does not get the chance to soak into
the soil and replenish the groundwater supplies, which dries
out soil and stresses remaining plants.
Introduced
genetic material;
Terrestrial fauna
The Green Iguana (Iguana iguana) on St. Maarten is thought to
be breeding with remaining populations of the Lesser Antillean
Iguana (Iguana delicatissima), resulting in hybrid population and
loss of the native species. On Saba, it is thought the native
species might be a subspecies – a Black Iguana, which is also
threatened with hybridisation with other species of Iguana now
prevalent on Saba.