Some of us are missing!

Do you miss the corals that are no longer on Buccoo Reef? No, but you would miss mangoes in season if there were no pollinators. In this International Year of the Reef, more corals are likely to disappear as the earth warms. Dr Anjani Ganase, marine ecologist, reminds us of other creatures endangered or already lost; and asks us to pay attention to the accelerating decline in biological diversity because of the ways that humans have changed the environment. 

May 18 was World Endangered Species Day; and May 22 International Day for Biological Diversity. The reality is, as we lose more endangered species, the result is the decline of biodiversity. It is estimated that since 1970 (International Union for Conservation of Nature, IUCN), global vertebrate populations have declined by at least 30 %. Scientists warn that continued decline will result in extinctions, even potentially the sixth mass global extinction event. Humans have significantly accelerated the extinction rates of wildlife over the last century: more vertebrate species died in the last century compared to (modelled) natural extinction rates. Since 1900, 468 vertebrate species have gone extinct - 69 mammal, 80 bird, 24 reptile, 146 amphibian, and 158 fish (Ceballos et al 2015). When a species has not been found for over 50 years, it is considered extinct. In the Caribbean, the most notable recent extinction is the Caribbean Monk Seal, with the last sighting of one in 1952; it was listed as extinct by officials from NOAA in 2008 (ScienceDaily 2008).

The critically endangered Acropora palmata branching coral stands alone on a seascape that was once packed with dense thickets of these corals 40 years ago. Disease wiped out most of these species throughout the Caribbean during the 1980s. Photo Credit, The Ocean Agency.

What about invertebrates and plants? While many organizations focus on monitoring vertebrate species numbers (~66,000 species recorded), plants species exceed vertebrate number by at least four times, and the invertebrate animal species make up about 80 % of the world’s biodiversity (1.4 million catalogued species of invertebrates, Collen et al 2012) with insects making up the largest portion, about one million species, compared to vertebrate species (62,000, Collen et al 2012). One fifth of all invertebrates are at risk of extinction (Borrell 2012). Specifically, in regard to insects, the estimated decline may be high as 80 % of insect populations in specific countries, such as Western Europe (Vogel 2017). Scientists have been tracking declines in the populations of honeybees and monarch butterflies (Vogel 2017). In regard to marine invertebrates, corals populations are dramatically declining with possible local extinctions because of habitat degradation and climate change.
The Caribbean Monk Seal, Monachus tropicalis, is already gone. Sketch from "The Fisheries and Fisheries Industries of the United States", by George Brown Goode (1887). 

The major cause of population declines and risk of extinction - apart from cases where organisms are over extracted - is loss of habitat. Shockingly, freshwater ecosystems have seen sharp declines of amphibian species as well as freshwater invertebrates such as crabs and slugs (Collen 2012). Many freshwater ecosystems have been physically altered, dammed, redirected or modified for human purposes. Nutrient pollutants alter the chemistry of the fresh water. And stream habitats are altered and fragmented. The groups most at risk of extinction are amphibians and invertebrates that rely on upstream–downstream connectivity of fresh water. 

Land clearing for crops and pastures is also dramatically reducing the natural biodiversity. The mobility of the organism populations, especially in isolated or island ecosystems, may be so severely curtailed that they may be unable to repopulate after a major disturbance. Creatures of island ecosystems in particular become unique over time, and become endemic (specialised and restricted to a specific place). If the habitat changes significantly or the population is decimated through disease, then repopulation by the same species may not be an option.

Among the major causes of species loss and eventual extinction are pollution, disease and the introduction of invasive species. Humans are constantly altering natural physical barriers and landscapes causing rapid changes in the ecology of marine and terrestrial habitats. Global travel and global trade have introduced species into habitats where there are no natural predators, and where their proliferation drastically alters the ecosystem. In the recent decade, the invasive and voracious lionfish is wreaking havoc on coral reefs in the Caribbean. In Trinidad, the Giant African Snail feeds on local vegetation and is very damaging to local crops.

Trinidad and Tobago is home to about 48 animal and plant species that are globally listed as near threatened or worse - vulnerable, endangered or critically endangered - according to the IUCN Red List. Of these listed species, endangered and critically endangered species are mainly in the fish, amphibian, coral and bird groups. These are also the groups most significantly in decline globally over the past 40 years. 

What are some critically endangered (CE) endangered (E) species found in Trinidad? On land, the majority are amphibians - Bromeliad-dwelling Treefrog (CE), Lesser Antilles Robber Frog (E), El Tucuche Tree Frog (E). In the marine environment, we are losing corals such as the branching Acropora species (CE) and the boulder star corals (E) both of which created much of the reef structure to Caribbean reefs. Also ecologically important fish and sharks include Groupers - Black Grouper (CE) and Nassau Grouper (CE) and Sharks - Daggernose Shark (CE) and Hammerhead sharks (E). An example of an endangered bird species is the Trinidad Piping-Guan (CE) (IUCN Red List 2017).

Unfortunately, much of the Red List assessed by IUCN is already outdated. Considering the rate of population decline and with global trajectory, it would not be surprising to see that some vulnerable species shifting may already be endangered. Conversely, there may be a few exceptions where populations are stable locally. However, even if the population of a species is stable in Trinidad and Tobago, there needs to be consistent monitoring at the international level. We should not think that animals/ habitats do not need active management until they’re threatened, since humans throughout history have yet to be capable of such foresight and predictions. Instead efforts need to be focused on preserving natural biodiversity at all costs on top of already minimal enforcement of penalties for illegal land clearing and poaching activities. 

Loss of biodiversity will be devastating for humans. We may not notice it for a while because we have grown out of the habit of being in nature. We certainly won’t notice it in the marine environment. We have to trust those who are monitoring and warning us, so that we can take action before we also lose those things that we depend on for food and livelihood. Far from a simple concept, biodiversity gives rise to the rich and complex ecosystems which sustain life, health, growth and well-being. As Trinbagonians, island people, we rely heavily on the environment to provide all our industries, agriculture, health, tourism, fisheries and recreation. (Global Biodiversity Outlook 2010). 


FURTHER READING:

Borrell, B. (2012) One-fifth of invertebrate species at risk of extinction; Freshwater snails and reef-building corals among threatened groups. Nature News

Ceballos, G., Ehrlich, P. R., Barnosky, A. D., García, A., Pringle, R. M., & Palmer, T. M. (2015). Accelerated modern human–induced species losses: Entering the sixth mass extinction. Science advances, 1(5), e1400253.

Collen B, Böhm M, Kemp R & Baillie JEM (2012) Spineless: status and trends of the world’s invertebrates. Zoological Society of London, United Kingdom

IUCN 2017. The IUCN Red List of Threatened Species. Version 2017-3. <http://www.iucnredlist.org>. Downloaded on 05 December 2017.


Secretariat of the Convention on Biological Diversity (2010) Global Biodiversity Outlook 3. Montréal, 94 pages

ScienceDaily (2008) National Oceanic And Atmospheric Administration (NOAA) "Caribbean Monk Seal Gone Extinct From Human Causes, NOAA Confirms." ScienceDaily. <www.sciencedaily.com/releases/2008/06/080608074828.htm>.

Vogel (2017) Where have all the insects gone? http://www.sciencemag.org/news/2017/05/where-have-all-insects-gone

WWF 2016 – Living Planet Report 2016 Summary




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