THREAT TO ECOLOGICAL BALANCES AND SURVIVAL THRESHOLDS

ANY ECOSYSTEM, NO MATTER HOW RESILIENT, CAN BE PUSHED TO A POINT OF NO RETURN OR, MORE EXACTLY, TO A THRESHOLD BEYOND WHICH LIMITING FACTORS BECOME A SEVERELY OPERATIVE THAT RECOVERY, IN PERIODS MEANINGFUL IN THE HUMAN TIME SCALE BECOME IMPOSSIBLE. FOR EXAMPLE, SOIL EROSION ON MOUNTAIN SIDES MAY REACH A POINT WHERE BED ROCK IS EXPOSED. WHEN THIS SITUATION TAKES PLACE, ONLY THE SLOW PROCESS OF PRIMARY BIOTIC SUCCESSION, WHICH HAVE BEEN OPERATING FOR CENTURIES OR MILLENNIA, CAN BUILD THE SOIL AND VEGETATION. ANOTHER THRESHOLD PROCESS, TYPICAL OF MANY AREAS, IS SOIL LATERIZATION, WHICH CAN ONLY BE ARRESTED ECONOMICALLY AT CERTAIN EARLY STAGES.ONCE A TOUGH LAYER OF LATERITE IS EXPOSED OR FORMED, RECOVERY MAY NO LONGER BE FEASIBLE. COMMUNITIES MAY REPAIR  THEMSELVES, WITH MODERATE PROTECTION, UP TO A CERTAIN POINT. BEYOND A CERTAIN LEVEL OF ABUSE OR DISTURBANCE, BIOLOGICAL REPAIR BECOMES, IN HUMAN TERMS, AN INTOLERABLY SLOW PROCESS.

CONSISTENT OVER-CROPPING OF ANY SPECIES CAN REDUCE ITS NUMBER TO LEVELS FROM WHICH RECOVERY IS NO LONGER POSSIBLE. KILLING THE LAST INDIVIDUAL ANIMAL OR CUTTING THE LAST TREE OF A SPECIES MAY NOT BE NEEDED  TO BRING ABOUT EXTINCTION. IF ANIMAL POPULATIONS ARE REDUCED TO A LEVEL AT WHICH EFFECTIVE BREEDING  DOES NOT OCCUR, OR IF THE HABITAT OF A SPECIES IS DESTROYED, RECOVERY WILL NOT TAKE PLACE, EVEN THOUGH SOME INDIVIDUALS WILL SURVIVE FOR SOME TIME. SIMILARLY FOR PLANTS, IF A MINIMUM AREA TO ENSURE REGENERATION OF CERTAIN SPECIES IS NOT MAINTAINED, THEY WILL EVENTUALLY DIE OUT. THE NUMBER OF INDIVIDUALS OR THE SIZE OF HABITAT NEEDED TO ASSURE SURVIVAL OF SPECIES HAS NOT YET BEEN GENERALLY DETERMINED. THE THRESHOLD  APPARENTLY  VARIES WITH THE GENETIC  MAKE-UP OF THE SPECIES,ITS HABITAT REQUIREMENTS AND BEHAVIOURAL CHARACTERISTICS.

PRODUCERS AND COSUMERS

PRODUCERS TAKE SIMPLE SUBSTANCES FROM THEIR ENVIRONMENT AND MAKE COMPLEX ORGANIC MOLECULES USING SOLAR ENERGY. ALL OTHER ORGANISMS MOLECULES USING SOLAR ENERGY. ALL OTHER ORGANISMS IN THIS WORLD ARE, DIRECTLY OR INDIRECTLY, DEPENDENTON THE PRODUCERS FOR THEIR FOOD.

THE WORLD DEPENDS ON FOOD MADE BY THE PRODUCERS AND, FORTUNATELY FOR US, PRODUCERS COME IN ALL TYPES AND SIZES, FROM MICROSCOPIC SINGLE-CELL ALGAE, SMALL PLANTS TO GIANT TREES.

CONSUMERS ARE ORGANISMS THAT FEED ON PRODUCERS OR OTHER ORGANISMS. THEY ARE CLASSIFIEDS AS FLLOWS :

• PRIMARY CONSUMERS OR HERBIVORES THAT FEED DIRECTLY ON PRODUCERS 
• SECONDARY CONSUMERS OR CARNIVORES THAT FEED ON OTHER CONSUMERS
• TERTIARY CONSUMERS THAT EAT OTHER CARNIVORES.

FOOD CHAINS AND FOOD WEBS

THE CONCEPT OF A FOOD CHAIN  SHOULD  BE INTUITIVELY CLEAR. THE FROG EATS THE INSECT, THE SNAKE SWALLOWS THE FROG EATS THE INSECT, THE SNAKE SWALLOWS THE FROG, AND THE SWOOPING HAWK FINISHES OFF THE  SNAKE. WE THUS HAVE A FOOD CHAIN. IT IS JUST A SEQUENCE OF ORGANISMS, IN WHICH EACH IS THE FOOD FOR THE NEXT. ALL ORGANISMS, DEAD OR ALIVE, ARE POTENTIAL SOURCES OF FOOD FOR OTHER ORGANISMS.

FOOD CHAINS OVERLAP, SINCE MOST ORGANISMS HAVE MORE THAN ONE ITEM ON THEIR MENU. AGAIN, AN ORGANISM COULD BE FOUND ON THE MENUS OF MANY OTHER ORGANISMS. THUS, WE HAVE A COMPLEX NETWORK OF INTERCONNECTED FOOD CHAINS  CALLED A FOOD WEB.

IF EVERY ORGANISMS MUST EAT ANOTHER ORGANISM FOR SURVIVAL, WHERE DOES THE FOOD CHAINS START? OBVIOUSLY THERE MUST BE AT LEAST ONE SELF-FEEDING ORGANISM THAT PRODUCES FOOD AND EATS IT TOO! SUCH PRODUCERS ARE IN FACT ALL AROUND US-THE GREEN PLANTS.

THE MAJOR THREATS TO BIRDS

• HABITAT LOSS AND FRAGMENTATION 
• INTRODUCTION OF NON-NATIVE SPECIES : BIRD-EATING SNAKES, RATS, CATS, MONGOOSE, ETC.; INSECTS AND PATHOGENS
• HUNTING AND CAPTURE
• COLLECTION FOR PET TRADE
• LONGLINE FISHING : THOUSANDS OF SEA BIRDS ARE CAUGHT IN HOOKS AND DROWN.
• OIL SPILLS
• PESTICIDES AND HERBICIDES
• SKYSCRAPERS,TOWERS, AND POWER LINES THAT KILL MILLIONS OF MIGRATORY BIRDS

BIRD LOVERS AND BIRDWATCHERS ALL OVER THE WORLD ARE TRYING TO SAVE THE WINGED WONDERS. THE FUTURE, HOWEVER, LOOKS BLEAK FOR BIRDS EVERYWHERE.

KILLING OF SHARKS IN USA

THE GROWING DEMAND FOR SHARK FINS AND SHARK MEAT, PARTICULARLY IN ASIA, HAS LED TO A RAPID ESCALATION IN SHARK FISHING. BETWEEN 1970 AND 2005, SHARK POPULATIONS HAS DECREASED BY 97 PER CENT ON THE EAST COAST OF THE US. THIS HAS UPSET THE BALANCE OF NATURE LEADING TO THE FOLLOWING SERIES OF EVENTS :

• WITH THE DROP IN SHARK POPULATION, THEY CAN NO LONGER PERFORM THEIR ECOSYSTEM ROLE AS TOP PREDATORS.
• AS A RESULT, THE POPULATION OF THE EAST COAST COWNOSE RAY HAS EXPLODED.
• THE HORDES OF RAYS CONSUME HUGE NUMBERS OF BAY SCALLOPS.
• THE FISHERS NOW FIND NO SCALLOPS TO HARVEST. THIS HAS ENDED A CENTURY-OLD NOTH CAROLINA OCCUPATION.
• OTHER RAYS, SKATE, AND SMALLER SHARK SPECIES HAVE ALSO EXPLODED IN NUMBERS. THIS IS CAUSING A CASCADE EFFECT THROUGH OUT COASTAL FOOD WEBS.

THE ONLY SOLUTION SEEMS TO BE  TO BAN SHARK FINNING BOTH IN NATIONAL WATERS AND ON THE HIGH SEAS.