This is not a scenario exclusive or unique to the oceans. In Kenya, within the Masai Mara reserve, a similar situation is taking place which has brought about a crash in the wild animal populations over the past 30 years. According to a study recently published in Journal of Zoology, researchers have determined that the number of impala, warthog, giraffe, topi, and hartebeest have declined by over 70%. Where huge herds of wildebeest would migrate from the Serengeti through the Mara region, their numbers have now dropped by 64% and the reserve's resident wildebeest population during the wet season has effectively disappeared, declining by as much as 97%.
"We were very surprised by what we found," said Dr. Joseph Ogutu from the University of Hohenheim, Germany and who headed up the study. "The Mara has lost more than two thirds of its wildlife."
In reaching their conclusions, the researchers combed through aerial photographs and monitoring data of animal herds and populations dating back to 1977. Over this 33-year period, they saw, among the 12 species of large animals, ostriches, and livestock studied, a drastic, relentless, and unexpected decline. Only a few species either within the reserve or just outside of its boundaries managed to maintain their numbers or show slight improvement. Since a major conservation effort was begun at the start of 2000, the researchers anticipated much greater improvement in the animal populations. But such was not the case.
To be sure, poaching has played a significant role in the decline, as it has in many developing nations. According to the BBC news, over 1500 poachers have been arrested within the Mara conservancy between 2001 and 2010, with more than 17,300 snares collected by rangers in the same period.
However, in addition to poaching, cattle grazing has played as great, if not greater, a role. The expansion of land used by ranchers for grazing, both within the reserve and outside its borders, has diminished the size and quality of wild animal habitat.
"Not only have numbers of cattle, sheep and goats increased but their distribution has widened, with the density of cattle increasing more than three-fold and that of sheep and goats more than seven fold up to 5km inside the reserve," Dr. Ogutu noted. "Sadly though, wildlife distribution has contracted throughout the entire Mara region in the same period."
Overgrazing impacts the natural fauna which can spill over into the remaining open land. The wild animal populations of the Mara region and, indeed, of all of Kenya, have evolved based on available area, quality of grazing land and food sources, and the animals' reproductive rates - all combine to make for a stable population. So, to put it simply, if you take away half the land, the animal population does not simply adjust and reduce itself by half. Instead, the once balanced system begins to collapse.
Just as industrial overfishing and degradation of marine habitat from development and population, when left unchecked or unregulated, can threaten marine ecosystems, so it is on the dry savannas of Kenya that poaching and expanding ranch land can threaten the rich animal diversity and expansive herds we have always come to associate with Africa.
The BBC News noted, "The expansion of settlements, fences and livestock numbers need to be regulated if these declines in wildlife are to be arrested, the researchers proposed, as well as bringing down poaching levels."
"Otherwise, the status of Masai Mara as a prime conservation area and premier tourist draw card in Kenya may soon be in jeopardy," said Dr Ogutu.