On the other hand, a community which has reached the point of culmination and which has experienced no form of release is likely to settle into a condition of stagnation. Its natural surplus of population is forced to emigrate. This type of emigration tends to occasion folk-depletion in the parent community. The younger and more enterprising population elements respond most sensitively to the absence of opportunities in their home town. This is particularly true when the community has but a single economic base, such as agriculture, lumbering, mining. Reformers try in vain to induce the young people to remain on the farms or in their native villages, little realizing that they are working in opposition to the general principles of the ecological order. Again, when a community starts to decline in population due to a weakening of the economic base, disorganization and social unrest follow.[46] Competition becomes keener within the community, and the weaker elements either are forced into a lower economic level or are compelled to withdraw from the community entirely. There are, of course, periodic and temporary fluctuations in the economic balance, due either to circumstances which affect the entire economic order or to the vicissitudes of the particular industry from which the community draws its sustenance. These temporary fluctuations, however, while important from the standpoint of social well-being, do not comprise the basic determinants of community development. The introduction of an innovating element into the adjustment of a community may be designated as the initial stage of an invasion which may make for a complete change in the structure and organization of the community. The introduction of a new mode of transportation, for instance, may transform the economic organization of a community and make for a change in population type. Thus the Harlem Railroad transformed Quaker Hill from a community of diversified farming, producing, manufacturing, selling, consuming, sufficient unto itself, into a locality of specialized farming. Its market had been Poughkeepsie, twenty-eight miles away, over high hills and indifferent roads. Its metropolis became New York, sixty-two miles away by rail and four to eight miles by wagon-road. With the railroad’s coming, the isolated homogeneous community scattered. The sons of the Quakers emigrated. Laborers from Ireland and other European lands, even negroes from Virginia, took their places. New Yorkers became residents on the Hill, which became the farthest terminus of suburban travel.[47]