Question: What are some of the causes that may make the wall to disappear in the next 20 years?
About the article "Great Wall of China", section "Condition".

Candidate passages:
While some portions north of Beijing and near tourist centers have been preserved and even extensively renovated, in many locations the Wall is in disrepair.
Those parts might serve as a village playground or a source of stones to rebuild houses and roads.
Sections of the Wall are also prone to graffiti and vandalism.
Parts have been destroyed because the Wall is in the way of construction.
More than of the wall in Gansu province may disappear in the next 20 years, due to erosion from sandstorms.
In places, the height of the wall has been reduced from more than to less than .
The square lookout towers that characterize the most famous images of the wall have disappeared completely.
Many western sections of the wall are constructed from mud, rather than brick and stone, and thus are more susceptible to erosion.
In August 2012, a section of the wall in north China's Hebei province collapsed after days of continuous heavy rains.
Records are not clear as to what the ship did next, but it may be presumed that she served in a support capacity for the duration of the Civil War.
Ultimately decommissioned at the Washington Navy Yard on 17 June 1865, "William Bacon" was sold at auction to William L. Wall and Co., on 20 July of the same year. 
Leukorrhea (US) or leucorrhoea (Commonwealth) is a medical term that denotes a thick, whitish or yellowish vaginal discharge.
There are many causes of leukorrhea, the usual one being estrogen imbalance.
The amount of discharge may increase due to vaginal infection or STDs, and also it may disappear and reappear from time to time, this discharge can keep occurring for years in which case it becomes more yellow and foul-smelling; it is usually a non-pathological symptom secondary to inflammatory conditions of vagina or cervix.
Vaginal discharge is not abnormal, and causes of change in discharge include infection, malignancy, and hormonal changes.
It sometimes occurs before a girl has her first period, and is considered a sign of puberty. 
There are apparent themes in this captivity narrative such as the uncertainty of life.
Rowlandson learns from the attack that no one is guaranteed life, and life can be short.
The stability of life including material things such as a house can disappear without warning at any given moment.
Rowlandson realizes that she is lucky to even be alive; that is why she does not take her own life.
During her captivity, she also finds that nothing is certain.
One day the Indians may be nice to her and treat her well, while the next day they may starve her without any explanation..
They might tell her one day she will be returned to her family while the next day she is dragged farther into the forest.
She cannot take anything for granted because she is not sure if she will even survive this long journey.
The next theme is the faith in God's will.
Throughout the whole experience, Rowlandson keeps her faith and returns everything that happens into a blessing or a doing of God.
"Yet the Lord still showed mercy to me; and as He wounded me with one hand, so he healed me with the other".
Much of this thought was common Puritan belief.
Puritans believed that God arranges everything with a purpose.
Rowlandson thinks humans have no choice but to accept the will of God and attempt to make sense of it.
She often compares Bible verses with situations in her own life.
She even believes the British troops did not defeat the Indians sooner because she and the Puritans have not yet learned their lesson, and therefore do not deserve victory.
Rowlandson learns that there is a thin line between savagery and civilization.
Her forced journey from civilization to the wilderness changes her perception on what is and what is not "civilized".
She first views civilization as things that are not savage and are not wild.
Naturally she depicts the Native Americans as violent savages but later the similarities of the Native Americans and the settlers become apparent to her.
Some of the Indians wear the colonists clothes and pray, claiming that they have converted to Christianity.
Rowlandson finds herself eating and enjoying the Indian food and often behaving like the Indians.
This causes savagery and civilization to be indistinct.
Because the narrative is from Mary Rowlandson's point of view, the story could be completely different if it were told by an outside observer.
This is the nature of a captivity narrative.
It has value, not because it is historically accurate, but because it captures the perceptions of an individual living through particularly harrowing historical experiences. 
The gameplay of "Snow Bros" is similar to "Bubble Bobble", released in 1986.
The game supports up to two players, with each player taking the part of one of two snowmen Nick and Tom.
Each player can throw snow at the enemies.
The player must throw snow at each enemy until it is completely covered, when it turns into a snowball.
An enemy partially covered in snow cannot move until it shakes it off.
Once an enemy has been turned into a snowball, the player can roll it.
The snowball will re-bound off walls, until eventually shattering against a wall.
Any enemies the snowball rolls into are eliminated and other stationary snowballs start rolling when the rolling snowball touches them.
If the player manages to take out all of the enemies with kicking one snowball (this one snowball may be used to make others bounce around as well and increase the chances to pull this trick off), money in the form of large green bills will fall from the sky.
These disappear in a very short amount of time but are worth 10,000 points each, the most the player can get as a bonus.
Every tenth level there is a boss.
Each boss can sustain being hit a number of times.
In Sega Genesis port, after the 50th level, you play as one of the snow castle princesses.
When a player bowls an enemy over, it may drop a potion bottle.
The color of the potion lets the player know what special power-up he or she will acquire: Red increases walking speed.
Blue increases amount of snow thrown, thus making it easier to cover an enemy in snow.
Yellow increases the distance that snow can be thrown.
Green causes your character to inflate like a balloon while having the ability to fly around screen and knock out enemies for a limited period of time.
The effects of the red, blue, and yellow potion wear off after the player loses a life.
If the player takes too much time to complete a level an evil pumpkin head will come and try to kill the player character.
It is invincible but can be stunned and sent to appear somewhere else in the level with snowballs or snow shots.
After a short time the evil pumpkin will spawn ghosts that can travel freely through the level and seek the player character.
These ghosts can't be killed or stunned, so the player's only hope is to avoid them while eliminating the rest of the enemies to move on to the next screen as soon as possible.
It is revealed in the NES ending that Nick and Tom are human princes.