By Joseph Penney
LAKE NAKURU, Kenya,(Reuters) - Lake Nakuru in Kenya is home to some of the world's most majestic wildlife: lions, rhinos, zebras and hundreds of bird species - including flamingos that famously blush the water pink when they gather in numbers
It is also home to Lake Nakuru National Park, one of Kenya's protected sites that safeguard the flora and fauna and help draw more than a million tourists a year to the East African country.
Nakuru is one of three shallow lakes - the others are Bogoria and Elementaita - lying in the part of Africa's Great Rift Valley that cuts a fertile gash through Kenya's highlands. The scenery is stunning, from forests of gentle green acacia trees to animals grazing on the grassy plain or congregating at the shores to drink.
The three lakes together are on UNESCO's World Heritage list of natural sites, especially prized for their bird life. That includes, the U.N. body says, "the single most important foraging site for the lesser flamingo anywhere," with hundreds of thousands of lesser flamingos moving between the three lakes.
Lake Nakuru, which lies about 170 km (105 miles) northwest of the capital Nairobi, is a fragile ecosystem, vulnerable among other things to the effects of rapid urbanization in the nearby city of Nakuru. The city is one of the largest in a country whose population more than doubled in the last 30 years, to around 45 million.
The population growth in Nakuru and in Kenya as a whole has also led to deforestation in the area in recent decades. The contrast in the landscape around the lake is clearly visible in NASA images taken from space in 1972 and this year, with many more homes and fewer trees now.
UNESCO says in its description of the three lakes region that with rapid population growth nearby, the area is under "considerable threat from surrounding pressures."
"These threats include siltation from soil erosion, increased abstraction of water in the catchment, degradation of land, deforestation, growth in human settlements, overgrazing, wildlife management, tourism and pollution coming from Nakuru town," the U.N. body says.
Deforestation is a contributing factor in floods, which perhaps surprisingly, are not always good for lakes.
In the case of Lake Nakuru, floods in 2011 expanded the shallow lake considerably and upset the chemical balance that is behind its ecosystem. More than a usual amount of water dilutes the alkaline level supporting the algae that flamingo feed on.
Christine Mwinzi, research scientist at the park, said the normal area of the lake was 31 square km (12 square miles) in 2010 and that had swollen to 54 square km (21 square miles) in 2013. In late 2014 it started receding but not quickly enough to return to the 2010 levels, she said.
The main entrance to the park was flooded and had to be moved up to an entrance on a hill. A trail that used to run around the lake shore was flooded and is no longer in use.
Mwinzi also mentioned sewage as an issue affecting the lake, again because Nakuru has grown and municipal services have not kept up.
(In December this year the U.N. Climate Conference takes place in Paris. Ahead of the summit, we will release a series of stories, titled "Earthprints," that show the ability of humans to change the landscape of the planet. From sprawling urban growth to the construction of new islands, each site has profoundly changed in the last 30 years. Each story has accompanying NASA satellite images that show the scale of the change.) (http://widerimage.reuters.com/story/earthprints-lake-nakuru)
(Writing by Frances Kerry; Editing by Brian McGee)