The problem is you need to decrease the top and bottom padding
property values:
form textarea
{
resize: none;
-webkit-appearance: none;
display: block;
border: 0;
background: #fff;
background: rgba(255,255,255,0.75);
border-radius: 0.50em;
margin: 1em 0em;
padding: 0.2em 1em;
height: 1em;
box-shadow: inset 0 0.1em 0.1em 0 rgba(0,0,0,0.05);
border: solid 1px rgba(0,0,0,0.15);
-moz-transition: all 0.35s ease-in-out;
-webkit-transition: all 0.35s ease-in-out;
-o-transition: all 0.35s ease-in-out;
-ms-transition: all 0.35s ease-in-out;
transition: all 0.35s ease-in-out;
font-family: 'Source Sans Pro', sans-serif;
font-size: 1em;
outline: none;
}